Markets and Prices

A market is an arrangement that lets buyers and sellers exchange things. They often exchange goods or services for money. The arrangement can be a store, a website, an auction, or a phone call.

Markets take many forms

A farmers market brings people together at a set place and time. An online store lets people buy from far away. A local market serves a town; a national market reaches across a country. A global market links buyers and sellers around the world. Coffee, oil, and smartphones reach buyers through global markets.

A buyer wants to get something; a seller offers it. A consumer buys for their own use. A producer makes goods or provides services. Goods are physical things, such as bread and sneakers. Services are tasks done for others, such as haircuts and bus rides. A music subscription provides a service even though no object changes hands.

Price, cost, and profit

A price is what a buyer pays for one unit. The seller's costs are what it spends to supply that unit. Ingredients, wages, rent, and energy all add to costs.

A pizzeria sells a slice for $3.50. Its costs for that slice total $2.00. Subtracting the costs leaves $1.50 of profit. The full $3.50 is sales revenue, not profit. If costs exceed the selling price, the seller makes a loss.

Why both sides agree

In voluntary exchange, each side expects to gain. People can value the same object differently.

Maya values a used bike at $90. Sam, its owner, values it at $50. They agree on a price of $70.

• Maya gets something worth $90 to her for $70. Her gain in value is $20.
• Sam receives $70 for something worth $50 to him. His gain is also $20.

The bike has not changed, but it now belongs to someone who values it more. The gains describe their own judgments. If the bike turns out to be worse than Maya expected, her expected benefit may not happen.

Money makes exchange easier

With barter, people swap goods directly. A baker who wants shoes must find a shoemaker who wants bread. That matching problem takes time.

With money, the baker can sell bread to one person and buy shoes from another. The baker and shoemaker no longer need to want each other's products. Money reduces the effort needed to trade.

Resources and time are limited: this is scarcity. People cannot make everything they want themselves. They specialize, focusing on particular work, and trade for other things. A baker can spend the day baking, then buy clothing and phone service from other producers.

The same person can buy in one market and sell in another. Identify what is being exchanged before deciding who is the buyer. A business is not always the seller.

Three kinds of market

In a product market, a family buys groceries from a store. Businesses also buy products, such as machines and ingredients. The name covers services too: paying for a movie ticket is a product-market exchange.

In the labor market, a café hires a server for $15 an hour. The café buys the server's work, so it is the buyer. The server sells time and skills. A wage is often stated per hour; a salary is usually stated per month or year. Both are prices paid for work.

In financial markets, savers supply funds and borrowers seek their use. Banks and other financial institutions connect people and businesses with funds. Interest is the price of borrowing. A borrower must repay the borrowed amount as well as the interest.

One person, several roles

A teenager earns money babysitting. She sells her work in the labor market. She then buys a concert ticket in a product market. When she saves some earnings at a bank, she participates in the financial sector.

Classify each exchange separately. Calling her a consumer describes her ticket purchase, but it does not describe the work she sells.

The chain from producer to consumer

Goods often pass through several businesses before reaching a shopper:

1. A farmer sells apples to a wholesaler for $0.40 each.
2. The wholesaler buys in large amounts and sells to a grocery store for $0.60 each.
3. The grocery store is a retailer. It sells to consumers for $1.00 each.

The wholesaler buys from the farmer and sells to the retailer. The retailer buys from the wholesaler and sells to the shopper. Each stage has its own market price.

The higher price at each stage helps pay for transport, storage, staff, and selling space. The difference between buying and selling prices is not all profit: other costs must be paid too.

The groups that take part

Economists call participants economic agents. They group them into households, businesses, financial institutions, and government. Households include people acting as consumers and workers. Government buys school supplies, road repairs, and teachers' work. It can also sell services, such as transit rides.

Buyers seek a price, quality, and level of convenience they can afford. Sellers seek enough revenue to cover costs and earn profit. A sale needs agreement from both sides.

The circular flow model shows exchanges between groups called sectors. Start with households and businesses. Households provide work and other resources; businesses use them to produce goods and services.

Two linked flows

When someone works at a bakery, work flows from the household to the business. Wages flow the other way. When that person buys bread, bread flows to the household and spending flows to the bakery.

Money and what it pays for travel in opposite directions. Household income can include wages, rent, interest, and profit. Household spending becomes businesses' sales revenue, the money received from sales.

A dollar is not used up when it is spent. It passes to someone else. A store can use a customer's payment to pay a supplier, who can use it to pay a worker.

Follow one month's income

Ana works at a bicycle factory and earns $2,400 a month. She divides that income between three uses:

Her $1,900 of spending becomes revenue for stores and other businesses. They use their revenue to pay workers, suppliers, and other costs. Her taxes and savings follow other routes through the economy.

Add banks and government

The financial sector includes banks and similar institutions. In this model, it connects savings with borrowing. The bicycle factory may borrow to buy a machine. Saving takes money out of immediate household spending; lending helps finance spending by borrowers.

The government sector collects taxes from households and businesses. It buys goods and services, pays public workers, and provides services such as roads and schools. It also makes payments to people, including retirement pensions and support after job loss.

A government payment is not always payment for current work. A teacher's salary pays for work; a retirement pension is a payment to a retired person.

Add other countries

The overseas sector represents trade with other countries. An export is sold to a foreign buyer and brings a payment into the economy. An import is bought from a foreign seller and sends a payment abroad.

Households, businesses, the financial sector, government, and the overseas sector form the five-sector model. It leaves out many details, but helps track where payments go.

Why the sectors depend on each other

The sectors are interdependent. Suppose households cut spending because they worry about the future. Stores receive less revenue and may reduce staff hours. Those workers earn less and may cut their own spending. One change spreads through several exchanges.

The chain can also run upward: more spending can bring more sales, work, and income. The people in households are also the workers, business owners, and public workers taking part in these flows.

Wanting something is not enough to buy it. Demand means the quantities buyers are willing and able to buy at different prices during a stated period. A demand table links each price with an amount.

Demand and quantity demanded

Someone may want a $1,200 laptop but lack the money to buy it. That wish adds nothing to quantity demanded at $1,200. At a lower price, the same person may be willing and able to buy.

Quantity demanded is the amount wanted at one particular price. Demand describes the whole relationship across prices. Keep the period clear: 70 boxes wanted on one Saturday means something different from 70 boxes wanted each month.

The law of demand

The law of demand says that, when nothing else changes, a higher price leads buyers to buy less. A lower price leads them to buy more.

Why does this happen? First, spending more on one good leaves less money for other things. Its opportunity cost, what the buyer gives up, rises. Some shoppers decide another use of their money matters more.

Second, buyers can switch to substitutes: goods that can replace one another. If strawberries become more expensive, some people buy apples instead. Some reduce their purchase without stopping completely.

Read a demand schedule

A demand schedule is a table of prices and quantities demanded. Here is market demand for boxes of strawberries at a Saturday market:

At $5, buyers want 50 boxes. If the price falls to $3, the table shows 90 boxes wanted. That is 40 additional boxes. Move to the row for the new price; do not add the quantities from both rows.

The table describes buyers' plans. It does not tell us how many boxes sellers offer or how many can actually be sold.

Add buyers at the same price

Market demand combines all buyers' quantities at each price. At $4, Lena wants 2 boxes, Omar wants 1, and Jess wants none. Together they want 3 boxes. A market table adds every buyer in this way.

Why the condition matters

The words "when nothing else changes" keep the comparison fair. A price rise during a heat wave may happen alongside a change in shopping plans. To see the effect of price alone, hold weather, income, and other influences steady.

Buyers also react by different amounts. A snack brand has many close substitutes, so shoppers can switch easily. A person who needs gasoline for work has fewer quick alternatives. A higher price can reduce purchases only a little in the short run.

Supply describes the quantities sellers are willing and able to offer at different prices during a period. Quantity supplied is the amount offered at one particular price. A supply table records sellers' plans, not buyers' wishes.

Why a higher price encourages supply

The law of supply says that, when nothing else changes, a higher price leads sellers to offer more. A lower price leads them to offer less.

Price matters because it changes the reward from selling. A grower spends $2.50 to grow, pick, and pack each box of strawberries. At a $2 selling price, she loses $0.50 per box. At $4, she earns $1.50 above that cost.

The higher price makes supplying boxes more attractive. Growers may pick more fruit, stores may order more stock, and new sellers may enter. When the price is too low to cover costs, some sellers reduce what they offer or stop selling.

Read a supply schedule

A supply schedule links each possible price with quantity supplied. This table shows boxes offered at the Saturday market:

At $3, growers offer 50 boxes. At $5, they offer 90. The $2 rise encourages 40 more boxes to be offered. The numbers rise as price rises, the opposite pattern from the demand table.

Market supply adds all sellers' quantities at the same price. If one grower offers 40 boxes and another offers 30 at $4, together they offer 70.

Supply needs time to respond

A higher price cannot make a new crop grow overnight. A farmer can bring more ripe fruit but cannot instantly enlarge the harvest. A factory may add working hours sooner than it can build another production line.

Over time, businesses can expand, and more sellers can enter. The response to a higher price can therefore be larger after months or years than after one day.

Stock and supply are related but different. Stock is what is available now. Supply tells us what sellers are willing and able to offer across different prices. Having stock does not mean offering it all at every price.

Sellers still need buyers

A seller chooses an asking price, but that does not guarantee a sale. A store charging more than nearby rivals may lose shoppers. Some shoppers will pay extra for better quality, convenient hours, or faster delivery.

When using the law of supply, keep costs and other influences unchanged. A higher selling price raises the reward for producing; higher ingredient or energy costs change the cost of producing. Those are different events.

Buyers and sellers respond to the same price in different ways. Put their quantities in one table to see whether their plans fit. The market price, or equilibrium price, is where quantity demanded equals quantity supplied.

Compare both sides

At $4, both sides plan to trade 70 boxes. The equilibrium price is $4 per box; the equilibrium quantity is 70 boxes. Total sales revenue is $280: 70 boxes sold at $4 each. Revenue is not profit, because growers still have costs.

At equilibrium, buyers willing and able to pay that price find the amount sellers offer. It does not mean everyone gets all the strawberries they would like for free.

Below equilibrium: a shortage

At $3, buyers want 90 boxes but sellers offer 50. The shortage is 40 boxes: the amount demanded minus the amount supplied.

People may line up or find empty stalls. Buyers compete for the available boxes, and sellers see that they can charge more. A rising price reduces quantity demanded and increases quantity supplied, moving toward the $4 matching row.

The shortage is not 90 boxes: some of the wanted boxes are available. It is also not the total of the two columns. It is the gap between them.

Above equilibrium: a surplus

At $5, sellers offer 90 boxes but buyers want 50. The surplus is 40 boxes: the amount supplied minus the amount demanded.

Unsold fruit may spoil, so sellers have a reason to cut prices. As price falls, buyers want more and sellers offer less. Both responses reduce the gap.

A method for any table

1. Read the price and both quantities from the same row.
2. If buyers want more, subtract supply from demand to find the shortage.
3. If sellers offer more, subtract demand from supply to find the surplus.
4. Find a row with equal quantities.
5. State the price per unit and the quantity, with their units.

If no row matches, the exact equilibrium may lie between the listed prices. Do not choose a row just because one number looks close to the price.

Adjustment in everyday markets

A grower who sells out early may raise the price next week. A grower taking unsold boxes home may lower it. Many separate decisions can move a market toward equilibrium without one person setting the price for everyone.

A fixed ticket price can stay below equilibrium. Tickets then sell out quickly, and resale prices may be much higher. A shortage is a gap at a particular price. Scarcity is the wider problem of limited resources and unlimited wants; it remains even when a market has no shortage.

A change in demand happens when something besides the good's own price changes buyers' plans. Buyers want more or less at every price. This changes the demand table itself.

What can change demand?

Income matters: people with more income buy more of most goods. Tastes, trends, and advertising can make a product more popular. Weather, seasons, and events also change plans. More visitors in town increase the number of buyers.

Expectations affect when people buy. Someone expecting a price rise next week may buy now. Someone expecting a price cut may wait.

Prices of related goods matter too:

• Substitutes replace one another. If movie tickets become more expensive, some people choose streaming, increasing demand for it.
• Complements are used together. Cheaper game consoles can attract more console buyers, increasing demand for games.

Keep the product clear. A rise in a movie ticket's own price changes quantity demanded for movie tickets. Its effect on streaming is a change in demand for a different product.

More demand: follow the shortage

At the strawberry market, the original equilibrium is $4 and 70 boxes. A sunny weekend brings more visitors. Buyers now want 40 extra boxes at every price; supply stays the same.

At the old $4 price, buyers want 110 but sellers offer 70. The shortage is 40 boxes. It pushes the price up. At $5 the quantities match at 90, so both the price and amount sold rise.

Sellers offer more because the higher price encourages them. The event first changed buyers' plans; the supply table did not change.

Less demand: follow the surplus

Now consider a different Saturday, starting again from $4 and 70 boxes. Cold rain makes buyers want 40 fewer boxes at every price.

At $4, buyers want 30 boxes while sellers offer 70. The surplus of 40 puts downward pressure on price. At $3, buyers want 50 and sellers offer 50. The new equilibrium is $3 and 50 boxes: price falls and less is sold.

A new table or another row?

A change in the good's own price means reading another row of the same demand table. A change in income, tastes, weather, or a related good's price can change the demand table.

This distinction prevents a circular explanation such as "the price rose, so demand fell, so the price fell." Begin with the outside event.

The same idea applies to jobs. If several new restaurants need servers, demand for servers rises. At the old wage there may be too few applicants, so employers offer higher pay to attract workers.

A change in supply happens when something besides the good's own price changes sellers' plans. They offer more or less at every price. Start by asking what happened to production, costs, or the number of sellers.

Events that change supply

Higher material, energy, wage, rent, or transport costs make production less rewarding. Sellers offer less at each selling price. Lower costs have the opposite effect.

Better technology can let a factory produce more at the same cost. More sellers entering a market also increase supply. A tax on producers raises their costs and decreases supply. A subsidy, a government payment to producers, can increase supply.

Weather and disruptions can reduce what sellers can offer. Frost can damage fruit; a fire can close a factory; a blocked shipping route can delay deliveries. A good harvest can increase farm supply.

Less supply: a damaged crop

Start from the strawberry market's equilibrium of $4 and 70 boxes. A storm damages the fields. Growers now offer 40 fewer boxes at every price; demand stays unchanged.

At the old $4 price, buyers want 70 boxes but growers offer 30. The shortage is 40. As the price rises, buyers reduce their purchases and sellers offer more from the smaller available supply. At $5, both quantities equal 50.

The new price is higher, but fewer boxes are sold. The higher price has not repaired the crop.

More supply: a large harvest

Consider a separate change, again from $4 and 70 boxes. A bumper harvest lets growers offer 40 extra boxes at every price.

At $4, supply is now 110 but demand remains 70. The surplus of 40 pushes the price down. At $3, buyers want 90 and sellers offer 90. Price falls while the amount sold rises.

Improved production methods can have the same direction of effect. Flat-screen televisions became less expensive as better methods and more manufacturers expanded supply.

Compare two reasons for a higher price

A higher price alone does not tell you which event occurred. With one side changing, the amount sold helps distinguish the two explanations.

A rise in production costs also does not mean sellers can add the whole increase to prices. Buyers may buy less or switch, and rivals may offer better deals. Sellers' wish for higher profit exists all along; explain a price change by identifying what changed in the market.

A useful explanation links an event to buyers or sellers, then to a gap at the old price. Saying "because of demand" leaves out the direction and the reason. Follow the chain through to the amount sold.

A six-part chain

1. Name the event.
2. Identify demand, supply, or both.
3. State whether each affected side increases or decreases.
4. Identify the shortage or surplus at the old price.
5. Predict the direction of price and the amount sold.
6. Join the steps with words such as "because" and "so."

Gasoline: rising input costs

Crude oil is the main raw material used to make gasoline. A complete price explanation is: "Crude oil became more expensive, raising refiners' costs. Gasoline supply fell, creating a shortage at the old pump price. The price rose and the amount sold fell."

Drivers buy a little less because many cannot quickly replace their trips to work.

Demand can change too. In many places, summer road trips raise gasoline demand. At the old price there is a shortage, so the price rises. This demand change pushes the amount sold upward, unlike the supply decrease.

When both sides change

Consider each change separately before combining them.

When the price pressures oppose each other, their relative sizes matter. The price can rise, fall, or stay the same.

At the strawberry market, a new growing method adds 40 boxes to supply at every price. A health trend adds 40 boxes to demand at every price. At $4, the old quantities of 70 both become 110. The price stays $4 while sales rise to 110 boxes.

Read the headline carefully

"Avocado prices jump after poor harvest" starts with a supply decrease. "Ticket prices soar as fans rush to see the final" starts with a demand increase. Trace the event, not just the words "prices jump."

Nearby sellers can also charge different prices. A gas station near several rivals faces drivers who can compare and switch. An isolated station faces less local competition and may charge more.

Inflation means a rise in the overall price level over time. One crop becoming expensive after a storm is an individual price change. During inflation, some individual prices can still fall.

An economy has limited workers, land, machines, and time. It must decide what to produce, how to produce it, and who gets the output. Prices help connect these decisions across many buyers and sellers.

What, how, and for whom?

In a market economy, buyers' and sellers' decisions guide production through prices.

• What? Businesses produce goods and services that buyers will pay enough for to cover costs and earn profit.
• How? Businesses seek methods that keep costs low, using workers, machines, or a mixture of both.
• For whom? Products go to people willing and able to pay the market price. Income affects that ability.

A product can be badly needed by someone who cannot afford it. A market price tells us about willingness and ability to pay together, not need alone.

A signal and an incentive

A signal provides information. A rising price points to a shortage at the old price, caused by more demand or less supply. A falling price points to a surplus at the old price.

An incentive gives someone a reason to act. A higher price encourages businesses to supply more when it makes production more profitable. A low price that leaves costs uncovered can push a business to cut production or leave.

Follow the resources

Oat milk becomes popular. Demand rises, creating a shortage at the old price. Its price rises, and producing it becomes more profitable.

Farmers plant more oats. Factories add production lines. New brands enter. Workers, land, and machines move toward making the product buyers want. Supply increases, easing the upward pressure on price.

Expansion takes time: a signal cannot instantly create a field or factory. Businesses respond through many separate decisions, without one office directing each move.

Losses send a different message. If too many bubble tea shops open, some may not cover their costs. When they close, their staff, space, and equipment become available for other work.

Prices ration limited goods

Rationing means deciding who gets a limited amount. Suppose a stadium has 1,000 seats and 5,000 fans want them. A high ticket price limits purchases to people willing and able to pay it.

This can allocate seats quickly. It can also exclude low-income fans who care deeply about the game. Societies debate the fairness of using ability to pay to distribute scarce goods.

Markets and government

Most countries, including the United States, have mixed economies. Markets guide many decisions, while government provides services such as public schools and roads and sets market rules, including a minimum wage.

In a command economy, government makes most decisions about what, how, and for whom to produce. These labels describe who mainly makes decisions; a mixed economy combines market decisions with government action.

Competition is rivalry for the same customers, goods, or workers. Sellers compete to win buyers. Buyers compete for scarce goods. Employers compete to hire people with the skills they need.

Price and non-price competition

Price competition attracts buyers through the amount they pay. Examples include a lower price, a discount, loyalty rewards, or a promise to match a rival's price.

Non-price competition attracts buyers through other features. Quality, design, a brand, helpful service, location, longer hours, fast delivery, and new features can all matter. Advertising can draw attention to these differences.

Two pizza shops charge $14 for a large pizza. Shop B cuts its price to $12. Some customers switch. Shop A can cut its own price or improve what customers receive. Free delivery or a better pizza may persuade some buyers to stay.

A price cut is easy to spot, but two shops with identical prices can still compete. A shopper may choose the one with better service or more convenient hours.

How many sellers are there?

Markets vary in the number of close competitors.

A market dominated by a few large sellers is an oligopoly. A market with one seller and no close substitute is a monopoly. The product and area matter: count the alternatives available for that purchase.

Buyers compete too

When several people want one house, they may offer higher amounts to win it. At an auction, buyers raise their bids against one another. Competition among buyers puts upward pressure on the price of the limited item.

Limited-edition sneakers can attract more willing buyers than there are pairs available. The scarcity of those pairs makes buyers' rivalry important, even if many stores sell other shoes.

Employers compete for workers

An employer buys labor. If workers can choose among jobs, an employer may need to offer higher pay, better hours, or extra benefits.

A new warehouse offers $19 an hour. Nearby stores paying $16 may raise pay to keep staff. If workers leave, the stores must replace them or reduce their hours of service.

When many people apply for the same job and there are few alternatives, employers face less pressure to offer more. Pay therefore depends partly on demand for workers and the supply of people willing and able to do the work. Better hours are non-price competition in this setting; higher wages change the price of labor.

Competition gives buyers alternatives. A business that offers poor value risks losing customers. This pressure can change prices, product quality, and how businesses use resources.

Lower prices and more choice

When buyers can compare and switch easily, a seller has less room to charge much more than rivals. Competition tends to push prices toward production costs plus a reasonable profit.

One airline charges $420 for a round trip. A second begins selling the same route for $300. The first lowers its fare to $310. A traveler using the first airline now pays $110 less.

This saving comes from a new alternative. The first airline has a reason to lower its fare because travelers can leave it for the rival.

Firms also serve different needs. One may offer a low-cost basic product, another a durable version, and another a special design. More choice can help buyers find something that fits their needs and budget.

Better quality and new ideas

If customers can walk away, firms have a reason to make products last longer or work better. Helpful service can keep customers returning.

Innovation means introducing new products, features, or production methods. A phone maker may improve its camera to attract buyers from rivals. A business may also invent a cheaper way to make its product.

Efficiency means using resources carefully and avoiding waste. A bakery that wastes less flour, energy, and staff time can lower its costs. It may then offer a competitive price while still earning profit.

Innovation and efficiency are connected but different. A new feature adds something; efficiency concerns how well resources are used. A business can improve one without improving the other.

Buyers help create the pressure

Comparison matters. If a shopper checks several stores and switches to a better offer, the seller has a reason to improve. Buyers who always use the same seller without comparing put less pressure on it.

Switching is easier when shoppers can see prices clearly and reach other sellers. A remote store may face less pressure than one beside several rivals.

Benefits have limits

Competition can force a small shop to close when a large chain opens nearby. A business may cut costs by lowering quality or workers' pay. A lower price alone does not tell us whether every change was beneficial.

Competition also does not prevent every price rise. If energy becomes more expensive for all bakeries, all face higher costs. Their prices can rise even while they continue competing.

To explain a change, identify both the pressure from rivals and what happened to costs or buyers' plans. Many sellers can limit an increase without keeping the price completely unchanged.

Competition is weaker when buyers have few close alternatives. New firms may struggle to enter, or existing rivals may agree to stop competing on price. These are different reasons for weak competition.

Monopoly and its limits

A monopoly has one seller and no close substitute. The seller faces less pressure to cut prices or improve service.

A stadium does not allow outside drinks. Inside, water costs $5.00; a store outside charges $1.50. The $3.50 difference can persist because fans cannot easily choose the outside drink while watching the game.

Market size alone does not define monopoly. A very large company may still face strong close rivals. A monopoly also cannot make buyers pay any amount: as its price rises, some buy less or go without.

What keeps new sellers out?

Barriers to entry make it hard for rivals to start selling. They include very high start-up costs, control of an important resource, limited licenses, patents, and strong loyalty to an established brand.

A patent lets its owner stop others from making, using, or selling an invention without permission for a limited time. This can restrict entry into that product's market.

Some services work best with one network. Building several sets of water pipes through the same streets could waste resources. Governments often regulate these suppliers' prices or run the service themselves.

Price fixing removes a choice

Price fixing is an agreement among competitors to raise, lower, or hold prices. A cartel is a group of firms coordinating such behavior.

Suppose three town bakeries secretly agree to charge $5 for a loaf. Customers still see three stores, but the stores have removed their independent price competition. The number of shop signs hides the agreement.

In the United States, competitors' price-fixing agreements are illegal. The Federal Trade Commission (FTC) and the Department of Justice enforce antitrust laws that protect competition. They can also challenge a merger, when companies join, if it would harm competition too much.

Matching is different from agreeing

Gas stations can watch each other's public price signs. One station may independently match another's price to keep customers. Similar prices alone are not enough to show that the owners agreed.

The key distinction is whether rivals made independent decisions or agreed with each other. Prices may also look alike because businesses face similar costs. Investigating price fixing requires evidence of an agreement, not just two matching numbers.

Protecting competition aims to preserve real alternatives. It does not mean stopping every business from growing or treating every merger as harmful.

Packages come in different sizes. A unit price shows the cost for the same amount, such as one ounce, one item, or 100 grams. It lets you compare the contents as well as the price tag.

Divide price by quantity

To find a unit price, divide total price by the number of units. Keep the unit beside the result. Dollars per ounce and dollars per pound are different measures.

A 12-ounce cereal box costs $3.60. Dividing $3.60 by 12 gives $0.30 per ounce. An 18-ounce box costs $4.86. Dividing $4.86 by 18 gives $0.27 per ounce.

The bigger box costs more today, but each ounce costs $0.03 less. For 36 ounces, three small boxes cost $10.80. Two large boxes cost $9.72, saving $1.08 for the same amount.

Use the same measurement unit

A shelf label of $0.25 per ounce cannot be compared directly with $3.80 per pound. One pound contains 16 ounces. So $0.25 per ounce is $4.00 per pound. At $3.80 per pound, the second product costs less for the same amount.

You can convert either price, provided both end in the same unit. Do the conversion before deciding which number is lower.

Compare metric packages

A 250-gram coffee bag costs $6.00; a 340-gram bag costs $7.48. To compare per 100 grams, first count the 100-gram units.

The larger bag costs $0.20 less per 100 grams. Dividing by 250 gives a price per gram, so label the result carefully if using that method.

Multipacks need checking too

A 6-pack of yogurt costs $4.50, or $0.75 per cup. Single cups are on sale at $0.69 each. The single cups are cheaper per cup even though the multipack looks like a bulk deal.

A reliable comparison

1. Choose one unit for both products.
2. Convert sizes or unit prices where needed.
3. Divide price by quantity.
4. Round the final prices to cents; keep more detail when they are very close.
5. Check whether you will use the amount you buy.

Dividing quantity by price gives units per dollar, not dollars per unit. That is a useful but different measure: more units per dollar is better, while fewer dollars per unit is better.

The lowest unit price can still mean spending more than your budget allows. Food that spoils before it is eaten also reduces the value of a bigger package.

A price tag may show only part of what you pay. Total cost includes the product, required fees, delivery, and any added tax, after discounts. Compare final amounts for the same purchase.

Percentage discounts

A jacket costs $48 with 25% off. Find the discount first: one quarter of $48 is $12. Subtract $12 from $48 to get a sale price of $36.

You can also find the part paid. A 25% discount leaves 75% to pay, and 75% of $48 is $36. The discount amount and the sale price answer different questions.

A sale label is not a comparison with every other store. A shirt marked "Was $60, now $45" still costs $3 more than the same shirt sold elsewhere for $42.

Include delivery and other fees

Headphones cost $34.99 online plus $5.99 shipping. The delivered total is $40.98. A local store sells the same headphones for $38.50, which is $2.48 less.

If collecting them adds travel costs, include those too. A $3 bus fare would make that trip cost $41.50 in total. Comparing only the product prices misses the cost of getting the purchase.

Read multi-buy deals carefully

"Buy one, get one 50% off" on $6 notebooks means the first costs $6 and the second $3. Together they cost $9, or $4.50 each.

Two full-price notebooks would cost $12. The $3 saving is 25% of that total. The deal is not 50% off both notebooks, and it requires buying two. If you need only one, buying the second increases what you spend.

Add sales tax where required

In most US states, sales tax is added at checkout. Rates vary by location, and the amount owed depends on the purchase. A shelf price can therefore be below the final amount.

For a $20 item with 7% tax, find 7% of $20: $1.40. Add it to get $21.40. In many other countries, the displayed price already includes tax, so adding it again would count it twice.

For a worked comparison, follow the offer's details about what is taxed and when discounts apply. If tax applies to the discounted product price, find that price first.

Compare subscriptions over equal periods

A plan at $9.99 a month costs $119.88 for 12 months. A yearly plan at $99 saves $20.88 for someone using the service all year.

A person needing only three months would pay $29.97 monthly. For that use, the $99 yearly plan costs more. Put both plans over the period you need before choosing.

Store websites, flyers, apps, and comparison sites help find offers. List the final costs side by side so a low advertised price cannot hide a larger payment.

Value for money means the benefit you get for what you pay. The lowest purchase price may not give the lowest cost over time. Quality, useful life, running costs, convenience, and your needs all matter.

Spread cost over use

Cost per use divides total cost by the number of uses. You can also compare cost per month when useful life is measured in months.

Sneakers costing $40 last 6 months. Their cost is about $6.67 per month. A $70 pair lasts 18 months, costing about $3.89 per month. The higher-priced pair offers a lower monthly cost if it really lasts that long.

The cheaper monthly result still requires $70 at purchase. A useful comparison includes both the long-term cost and what the buyer can afford now.

Include running costs

A printer's price is only the start. Compare the cost of producing the same number of pages.

For 2,000 pages, printer A costs $60. Its $30 cartridges print 200 pages each. It needs 10 cartridges costing $300, so the total is $360.

Printer B costs $120. Its $20 cartridges print 500 pages each. It needs 4 cartridges costing $80, so the total is $200. The higher-priced printer costs $160 less overall for those pages.

The page count must stay the same in both calculations. Comparing one printer for 500 pages with another for 2,000 would answer a different question.

Judge quality using evidence

Check what the product includes, how long its warranty lasts, and what independent reviews report. A famous brand may cost more without providing better quality. A store brand may meet the same need for less.

Useful life matters only if the product stays useful to you. Paying for extra features brings little value when you never use them.

Convenience has a cost and a benefit

Driving 20 minutes each way to save one dollar uses time and gasoline. That trip has an opportunity cost: other things you could do with the time and money.

An open-late corner store may charge more than a large supermarket. Some shoppers choose it because it saves a trip or is open when they need it. Different locations, rent, service, and competition help explain different prices for the same product.

Make a decision that fits the need

First decide what you need and can afford. Then list a few suitable offers. Work out final cost and any useful unit price or cost per use. Compare quality, likely life, and running costs before choosing.

A bargain on an unused product is extra spending.