Option delta
Option delta is the sensitivity of an option's price to a one-unit move in the underlying, expressed between 0 and 1 for calls and between -1 and 0 for puts. It also serves as the hedge ratio: the amount of underlying a delta-neutral hedger holds against the option position.
Senzoukria · Glossary · Updated September 2026
Three ways the same number is used
- Price sensitivity: a call with delta 0.40 gains about 0.40 per one-point rise in the underlying, holding everything else fixed.
- Hedge ratio: a hedger short that call holds about 0.40 units of underlying per contract, scaled by the multiplier, to stay delta-neutral.
- Moneyness label: options are often referred to by their delta rather than their strike. A 25-delta put is the put whose delta is closest to -0.25, whatever its strike happens to be that day.
Why delta moves
Delta is not fixed. It changes with spot (that rate of change is gamma), with implied volatility (vanna) and with time (charm). An at-the-money option sits near 0.50 and its delta is the most sensitive to spot; deep in-the-money options approach 1 and deep out-of-the-money options approach 0. Near expiry, the transition between those extremes narrows, which is why short-dated at-the-money options force the largest hedge adjustments.
Option delta is not orderflow delta
The word delta has a second, unrelated meaning on a footprint chart: volume executed at the ask minus volume executed at the bid at a price level. That delta describes aggression in the futures book; option delta describes a derivative's sensitivity. Senzoukria's documentation keeps the two apart, and a reader should too. A bar with strong positive footprint delta says nothing about the delta of an option position, and vice versa.
In Senzoukria
The GEX module's header shows a 25Δ skew figure, marked computed when it is built from the implied volatility of the 25-delta call and the 25-delta put; the volatility skew guide on this site describes that risk-reversal convention. Delta also drives the module's hedging reading: the Dealer positioning setting in Calculation assumptions decides the sign applied to each position, and the regime messages describe how a long-gamma or short-gamma book adjusts its delta hedge as spot moves. Footprint delta lives elsewhere: in the Delta footprint cell type and in the Delta Histogram indicator (bar delta) on the chart.
Common mistakes
- Reading a 0.30 delta as a 30% probability of expiring in the money. The two are related under some models but are not the same quantity.
- Assuming a dealer's hedge equals the delta of one option. The hedge is on the net book, which the public cannot see.
- Mixing footprint delta and option delta in the same sentence without saying which one is meant.
Related
This page in other languages
Frequently asked questions
- What does a 25-delta option mean?
- It is the strike whose delta is closest to 0.25 for a call or -0.25 for a put on a given expiry. Skew and risk-reversal measures compare the implied volatility of those two options because they sit at comparable distances from spot on each side. The actual strike shifts as spot and volatility change.
- How is option delta related to gamma exposure?
- Gamma is the change in delta per unit move in spot, and gamma exposure scales that gamma by position size. So GEX is an estimate of how much delta, and therefore how much hedge, a modeled book must adjust for a given move. Without a positioning assumption the sign of that adjustment is unknown.