Irish Calculators
Business

Price Elasticity Calculator for Demand Analysis

Calculate how the observed quantity change relates to a price change under your chosen percentage method. Other influences on demand are not controlled, so the result is descriptive rather than a sales forecast.

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Your numbers

Your figures stay on this device.

How the calculation works

Measure the observed responsiveness of quantity demanded to a price change between two commercial observations. Choose midpoint or initial-base percentages explicitly, because the denominator convention changes the calculated elasticity.

Elasticity = percentage change in quantity / percentage change in price. Initial-base percentages use the first observation; midpoint percentages use the mean of the two observations.

  1. Measure the quantity change

    Subtract initial quantity from final quantity. Divide by either average quantity or initial quantity according to the selected convention.

  2. Measure the price change

    Apply the same percentage convention to the two prices. A zero price change cannot support an elasticity ratio, even when quantity changed.

  3. Relate the two changes

    Divide the percentage quantity change by the percentage price change. The sign is retained. The revenue comparison separately multiplies each observation's price by its quantity.

Worked example: Midpoint response

Sample inputs demonstrate the method. They are not a forecast or product offer.

Price rises from €10 to €12 and quantity falls from 100 to 80. Midpoint changes are 18.1818% for price and minus 22.2222% for quantity, giving elasticity about minus 1.2222. Revenue changes from €1,000 to €960.

Percentage-change method
Midpoint (arc elasticity)
Initial price
10
Final price
12
Initial quantity demanded
100
Final quantity demanded
80

Expected result

Price elasticity
-1.2222
Final revenue
€960.00
Worked example: Initial-base response

Sample inputs demonstrate the method. They are not a forecast or product offer.

Percentage-change method
Initial-value base
Initial price
10
Final price
12
Initial quantity demanded
100
Final quantity demanded
80

Expected result

Price elasticity
-1

Understanding your result

The magnitude describes the relative changes in these observations. A negative result means price and quantity moved in opposite directions; it does not establish that price was the only cause.

Promotions, seasonality, product availability and customer mix may also change demand. This two-point measure does not estimate a statistical demand curve or guarantee results at an untested price.

Questions you might have

Why do the two price elasticity methods differ?

Initial-base changes depend on which observation is first. The midpoint method uses both observations symmetrically and is useful for larger discrete changes.

Choosing the right inputs

Percentage-change method
Midpoint uses the average of the two observations as each percentage base. Initial-base mode measures both changes relative to their starting values.
Initial price
Enter the initial unit price on the same currency and tax basis as the final price. Prices should refer to comparable products or offers.
Initial quantity demanded
Enter initial quantity demanded, matching the final observation's measurement period and unit. Different period lengths can distort the comparison.

Common mistakes to avoid

  • Do not mix midpoint quantity percentages with initial-base price percentages.
  • Do not compare monthly sales with annual sales or gross prices with net prices without first making the inputs comparable.

Assumptions to check

  • Use comparable quantities over comparable periods. Other influences on demand are not controlled.
  • Zero change in the explanatory variable has no defined elasticity.

Sources and method

Read our calculation and testing approach.