Enter quantity demanded for Good X and price for Good Y, before and after, to calculate cross-price elasticity.
How to Use the Cross-Price Elasticity Calculator
Enter Good X's quantity demanded before and after, and Good Y's price before and after — the elasticity value and a substitute/complement label are computed from the four numbers.
Cross-price elasticity measures how demand for one good reacts when the price of a completely different good moves — the textbook example being butter and margarine, where a jump in margarine's price nudges some shoppers toward butter instead.
% Change in Qx = (Qx₂ − Qx₁) ÷ ((Qx₂ + Qx₁) ÷ 2) × 100
% Change in Py = (Py₂ − Py₁) ÷ ((Py₂ + Py₁) ÷ 2) × 100
Cross-Price Elasticity = % Change in Qx ÷ % Change in PyThis calculator uses the midpoint (arc elasticity) method for both percentage changes rather than dividing by the starting value alone — the midpoint formula gives the same elasticity whether you're measuring a price rise or the identical price fall in reverse, which the simpler point-elasticity version doesn't.
The sign is the whole story: a positive value means the two goods are substitutes — Good Y got pricier and buyers shifted toward X. A negative value means they're complements, moving together instead — X's demand fell right alongside a price hike in something that's normally bought with it, like coffee and coffee filters. A value close to zero (under roughly 0.05 either direction) suggests the two goods aren't meaningfully related in demand at all.