Elasticity of Demand — Formula Sheet

E_{d}=\frac{\text { Percentage change in quantity demanded }}{\text { Percentage change in price }}

E_{d}=\frac{\frac{\Delta Q}{Q}}{\frac{\Delta P}{P}}=\frac{\Delta Q}{Q} \times \frac{P}{\Delta P}

\mathrm{TE}=\mathrm{P} \times \mathrm{Q}

When quantity demanded does not change at all with a change in price, demand is perfectly inelastic and Ed = 0.

When percentage change in demand is equal to percentage change in price, Ed = 1.