Delta

Delta measures how much an option's price changes for every $1 move in the underlying stock. A delta of 0.50 means the option gains or loses $0.50 for each $1 the stock moves. Call options have positive delta (0 to 1.0). Put options have negative delta (0 to -1.0).

Why It Matters

Delta is the most used Greek because it serves multiple purposes. It tells you your directional exposure — how much you stand to gain or lose from a stock price change. It serves as a rough proxy for the probability of an option expiring in the money. And it helps you size positions: a portfolio with a total delta of 200 behaves like owning 200 shares of stock.

Professional traders think in terms of delta before anything else. When they say "I'm long 500 delta," they mean their portfolio will gain $500 for every $1 the underlying rises.

How It Works

Delta values depend on moneyness:

• Deep ITM options: Delta approaches 1.0 (calls) or -1.0 (puts). They move nearly dollar-for-dollar with the stock.
• ATM options: Delta is approximately 0.50 (calls) or -0.50 (puts). They capture about half of the stock's move.
• Deep OTM options: Delta approaches 0. The option barely responds to small stock price changes.

Delta as probability: A 0.30 delta roughly indicates a 30% chance the option expires ITM. This is an approximation, not an exact probability, but it is widely used for quick strike selection.

Delta changes over time and with price movement. As expiration approaches, ATM options stay near 0.50 while ITM options move toward 1.0 and OTM options move toward 0. Gamma measures this rate of change.

Position delta for multi-leg strategies:

• Long 1 call (0.50 delta) = +50 delta (per contract, 100 multiplier)
• Short 1 put (-0.40 delta) = +40 delta (selling a negative delta is positive)
• An iron condor might have near-zero total delta (market neutral)

Quick Example

You buy one ATM call on stock PQR ($100 stock, $100 strike) with delta 0.52. The stock rises $2 to $102. Your option gains approximately $1.04 (0.52 x $2). Since you control 100 shares per contract, that's a $104 gain.

If you bought 5 contracts, your position delta is 260 (5 x 0.52 x 100). A $1 stock move means roughly $260 in portfolio change. That is equivalent to the directional exposure of owning 260 shares.