Calculating Price Elasticity of Demand

How to calculate price elasticity of demand.

price-elasticity-demand-formula Price elasticity of demand = % change in Q.D. / % change in Price

  • To calculate a percentage, we divide the change in quantity by initial quantity. If price rises from $50 to $70. We divide 20/50 = 0.4 = 40%

Example of calculating PED

When the price of CD increased from $20 to $22, the quantity of CDs demanded decreased from 100 to 87.

What is the price elasticity of demand for CDs?

Calculating a Percentage

  • The price increases from $20 to $22. Therefore % change = 2/20 = 0.1 (10%)
    0.1 = 10% (0.1 *100)
  • Quantity fell by 13/100 = – 0.13 (13%)
  • Therefore PED = -13/10
  • Therefore PED = -1.3

In this case demand is price elastic.

  • Therefore Demand is elastic. Elastic demand occurs when % change in quantity is greater than % change in price; when PED >1

Example 2

ped-elasticity i

  • Price rises from $15 to $30 (100% rise in price)
  • Quantity falls from 100 to 80 (20% fall)
  • PED – -20/100 = -0.2

Example 3


In this case the PED

  • % change in QD = -50/100 = 0.5 = -50%
  • % change in price =10/50 = 0.2 = 20%
  • Therefore PED  = -2.5

Example 4


PED = -10/40 = -0.25


Advanced – the difference between point and arc elasticity of demand

  1. Point elasticity of demand takes the elasticity of demand at a particular point on a curve. (using calculus to measure slope of curve)
  2. Arc elasticity measures elasticity at the mid point between the two selected points:

See also:

19 thoughts on “Calculating Price Elasticity of Demand”

    • the price of a notebook is 20 and the quantity bought weekly is 100units. and when the price rises to 150, the quantity demanded is 750uniys. calculate the co-efficient of the price elasticity of demand and state the type of elasticity

  1. u should explain unit elasticity sith mathematical calculation and graphical as well. and rest of the elasticity =œ and elasticity =0.thanks.

  2. Please explain why you are not dividing by the average quantity demanded or the average price. In the first example you are dividing by the original quantity and the original price. My text book states the correct equations is
    (change)Qd /Qdaverage /(change)P/ P average –(which states the change in quantity demanded over the average of the old and new quantity demanded then that is divided by the change in price over the average of the old and new price

  3. Given Rs.50, 000 (Fifty Thousand), explain in words, which goods having elastic demand, inelastic demand and unit elastic demand would you purchase with this amount. Now think about the producers of these goods. To increase their revenue, explain in words, should they increase or decrease the price of their products?

  4. Rohan is appointed an economics ’professor in a reputed university. In his first lecture, students asked him to elaborate on Gross Domestic Product (GDP) and Gross National Product(GNP). Help Rohan to prepare his first lecture on the given topic with relevant example and highlight the differences between the two concepts.

  5. The demand and supply for an economic textbooks are given by q=20-p and q=3p,respectively. a.what are the equilibrium price and quantity.imagine that government imposes a per-unit tax of $4 on the sellers

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