Delta

In plain words

Delta roughly tells you how many shares your options position is "worth" — a delta of 0.50 behaves in price like 50 shares.

In more detail

Delta measures how much an option's price changes when the underlying moves one unit. It has three readings, all used in trading: as price sensitivity, as a hedge ratio, and as a rough proxy for the probability of expiring in the money. Decisively, delta is not itself constant — it changes with the price, which is what gamma describes and what makes dynamic hedging necessary in the first place.

Formula

Δ = ∂V/∂S

The partial derivative of the option price V with respect to the underlying's price S.

Example

A call with a 0.40 delta gains roughly 0.80 euros on a 2 euro upward move. If the underlying keeps rising the delta grows to 0.55 — the next 2 euros then bring 1.10.

What it means for traders

The basis for delta hedging and position-sizing decisions in options portfolios.

Common pitfalls

Delta is only a linear approximation — for larger price moves, it becomes increasingly inaccurate due to gamma.

Related terms

Call Option · Charm · Deep in the Money · Delta Hedge · Delta Hedging · Delta Neutral · Gamma (Γ) · Lambda (λ) · Position Delta · Probability of Profit (POP) · Vanna