Price Elasticity of Demand GCSE: What It Means, How to Calculate It and Why It Matters

Price Elasticity of Demand - PED for short - is one of those GCSE Economics topics that looks harder than it is. The formula is simple. The calculation is straightforward. What actually trips students up is applying the concept to a business scenario and interpreting what the result means.

This guide is structured around that distinction. By the end, you will be able to calculate PED, correctly identify elastic and inelastic demand, and explain what a PED value means for a business's revenue decisions.

What Price Elasticity of Demand Measures

PED measures how sensitive the quantity demanded of a product is to a change in its price. If a product's price rises by 10% and quantity demanded falls by 20%, consumers are very sensitive to the price change - demand is elastic. If price rises by 10% and quantity demanded only falls by 2%, consumers are barely affected - demand is inelastic.

The concept was developed by economists to help explain and predict how markets behave, but for GCSE purposes the most important application is what it tells a business about its pricing decisions.

The Formula

PED = Percentage change in quantity demanded divided by percentage change in price

The result will almost always be a negative number, because when price goes up, quantity demanded goes down (and vice versa) - they move in opposite directions. Convention in economics is to report PED as the absolute value (dropping the minus sign), so a PED of -1.5 is typically referred to as 1.5.

An example: a coffee shop raises the price of its medium latte from £3.00 to £3.60 - a 20% increase. Sales fall from 200 to 160 cups per day - a 20% decrease. PED = -20% divided by +20% = -1 (or 1 in absolute terms).

Elastic and Inelastic Demand

The value of PED tells you which category demand falls into:

If PED is greater than 1 (for example, 1.5 or 2.3), demand is elastic. Consumers are relatively sensitive to price changes. A price rise leads to a proportionally larger fall in quantity demanded.

If PED is less than 1 (for example, 0.3 or 0.8), demand is inelastic. Consumers are relatively insensitive to price changes. A price rise leads to a proportionally smaller fall in quantity demanded.

If PED equals exactly 1, demand is unit elastic. The percentage change in quantity demanded exactly matches the percentage change in price.

For GCSE, you do not often encounter PED = 1 in exam questions - elastic and inelastic are what you need to be confident with.

What Determines Whether Demand is Elastic or Inelastic

This is a common GCSE question: "Explain two factors that affect the price elasticity of demand for a product."

Availability of substitutes. If close substitutes exist, consumers can switch to them when a price rises. This makes demand more elastic. Petrol has fewer close substitutes than a specific brand of fizzy drink - so demand for petrol tends to be more inelastic than demand for a branded soft drink.

Necessity versus luxury. Products people need regardless of price - prescription medication, energy for heating - tend to have inelastic demand. Luxury items that consumers can choose to go without tend to have more elastic demand.

Proportion of income. If a product is a small proportion of a consumer's income (a box of matches, a newspaper), price changes have little impact on purchasing decisions and demand tends to be inelastic. If a product represents a large proportion of income (a car, a holiday), consumers pay more attention to price and demand is more elastic.

Brand loyalty. Strong brand loyalty reduces the impact of price rises on demand, making it more inelastic. If someone is loyal to one brand of trainers, a moderate price rise might not change their purchasing decision - whereas a consumer with no brand preference will switch to the cheaper option.

What PED Means for Revenue

This is the part GCSE exam questions test most heavily, and it is where students most often drop marks.

The key rule: a business maximises revenue by cutting prices when demand is elastic and raising prices when demand is inelastic.

Here is the logic for elastic demand. If PED is 2 and a business cuts price by 10%, quantity demanded rises by 20%. Revenue = price times quantity. Price fell by 10% but quantity sold rose by 20% - so total revenue goes up. Cutting prices when demand is elastic increases revenue.

For inelastic demand, the reverse applies. If PED is 0.4 and a business raises price by 10%, quantity demanded falls by only 4%. Revenue = higher price times slightly lower quantity - overall, revenue goes up. Raising prices when demand is inelastic increases revenue.

Many students try to memorise this as a rule without understanding why it works. The logic - that the proportional change in quantity is what determines whether revenue rises or falls - is worth understanding properly, because exam questions often vary the scenario to test genuine comprehension rather than recalled rules.

The ClearConcept price elasticity tool (/tools/business/price-elasticity-demand/) lets you input a PED value and price change and see the revenue impact calculated immediately. Practising with different values makes the relationship between PED and revenue intuitive rather than something you have to think through each time.

A Common Misconception: Inelastic Does Not Mean Perfectly Inelastic

Students sometimes read "inelastic demand" as meaning consumers do not respond to price at all. This is not correct.

Inelastic demand means the percentage change in quantity demanded is smaller than the percentage change in price - not that there is no change. If petrol prices rise by 20%, most drivers will still fill their tanks, but some will cut discretionary journeys. Quantity demanded falls - just by less than 20%.

The distinction matters because exam questions might ask you to evaluate a firm's decision to raise prices. Even if demand is inelastic, you need to acknowledge that some customers will be lost and that very large price rises could move demand from inelastic to elastic territory.

How GCSE Exam Questions Use PED

Most PED exam questions follow one of three patterns:

Calculate PED from figures given. Use the formula: percentage change in quantity demanded divided by percentage change in price. Show your working clearly. State whether the result indicates elastic or inelastic demand.

Explain the effect on revenue of a price change. State the PED value given, identify whether demand is elastic or inelastic, apply the revenue rule (elastic: cut prices to increase revenue; inelastic: raise prices to increase revenue), and explain why using the proportional change logic.

Evaluate a business decision. You might be given a scenario where a business raises prices, told the PED value, and asked to assess whether this was a good decision. Use the PED rule, but also consider whether there are factors beyond price elasticity - competitor responses, impact on brand perception, long-term customer retention - that should inform the decision.

Running Through a Worked Example

Question: "A business sells 500 units of a product per week at £10 each. It raises the price to £12. Sales fall to 400 units per week. (a) Calculate the PED. (b) Is demand elastic or inelastic? (c) Explain the effect on the business's revenue." (6 marks)

(a) Percentage change in price: (£12 - £10) divided by £10 = 20%. Percentage change in quantity: (400 - 500) divided by 500 = -20%. PED = -20% divided by 20% = -1 (absolute value: 1).

(b) PED of 1 is unit elastic - neither elastic nor inelastic.

(c) Revenue before: 500 multiplied by £10 = £5,000. Revenue after: 400 multiplied by £12 = £4,800. Revenue has fallen slightly. When PED = 1, the proportional fall in quantity demanded exactly matches the proportional rise in price, so revenue should theoretically be unchanged - the small difference here is due to rounding in the percentage calculations.

Practising PED for the Exam

The best revision approach for PED is worked examples. Do the calculation, check it, then practise explaining the revenue implication in full sentences. The ClearConcept flashcard quiz (/tools/business/flashcard-quiz/) covers elasticity definitions and the factors affecting PED - useful for the recall elements of exam questions.

For the broader Economics context, the guide at /gcse-economics-revision-tips covers PED alongside supply and demand diagrams, government intervention, and the other topics that connect to it in the AQA spec.