Updated 2026-07-25
Delta measures how much a position's value changes when the underlying price moves by one unit. A perpetual or futures position is linear, so one contract of long exposure has a delta of one contract. Options are where delta becomes interesting: a call's delta runs from near zero far out of the money to near one deep in the money, and puts run negative over the same range.
Two practical uses. First, delta converts an options book into an equivalent underlying position, which is how a desk knows its true directional exposure. Second, delta changes as price moves, and the rate of that change is gamma. That second-order effect is why hedging flows can amplify or dampen moves near large strikes, and it is the link between options positioning and the spot market that liquidation traders care about.