The formula of Price elasticity of demand is the measure of elasticity of demand based on price, which is calculated by dividing the percentage change in quantity (∆Q/Q) by percentage change in price (∆P/P) which is represented mathematically as Price Elasticity of Demand = Percentage Change in Quantity (∆q/q) / Percentage Change in Price (∆p/p)

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%

To calculate price elasticity, divide the change in demand (or supply) for a product, service, resource, or commodity by its change in price. That figure will tell you which bucket your product falls into. A value of one means that your product is unit elastic and changes in your price reflect an equal change in supply or demand.