Unit-Elastic Demand
Plain definition
Demand is unit-elastic when quantity demanded changes by exactly the same percentage as price — price elasticity equal to 1 in absolute value. Any price change leaves total revenue (price times quantity) unchanged, because the price and quantity effects cancel out.
In economics
Unit elasticity is the boundary between elastic and inelastic demand and a useful benchmark in revenue analysis: raising price increases revenue while demand is inelastic, decreases it once demand turns elastic, with the revenue maximum at the unit-elastic point. Along a linear demand curve, elasticity falls from elastic to inelastic, passing through unit elasticity at the midpoint.
Example
On the unit-elastic demand curve quantity = 1,000,000 divided by price, cutting price from 100 to 80 rupees raises buyers from 10,000 to 12,500 — and revenue stays exactly 1,000,000 rupees either way. Price and quantity move in perfect offset.
Unit-elastic is often confused with quantity changing by the same number of units as price. It is percentage changes that match, not absolute units: a 10-rupee fall matched by 10 extra units is not unit-elastic unless those are equal percentage moves. That is why elasticity uses percentages, not raw differences.