Options Greeks: Delta, Gamma, Theta, Vega
The Greeks measure how option prices respond to stock price, time, volatility, and interest rates, helping traders manage risk.
Options Greeks: Delta, Gamma, Theta, Vega
The Greeks are the metrics that describe how an option's price changes in response to underlying variables. They are the dashboard of options trading — once you can read them, you can understand why your position gains or loses and how to manage risk.
The Four Main Greeks
| Greek | Measures | What It Tells You |
|---|---|---|
| Delta | Stock price change | How much the option moves per $1 in stock |
| Gamma | Delta's rate of change | How fast delta itself changes |
| Theta | Time decay | How much value is lost per day |
| Vega | Implied volatility | How much price changes with 1% IV move |
Delta (Δ)
Delta has two interpretations:
- Price sensitivity — A 0.50 delta means the option moves $0.50 for every $1 move in the stock
- Probability of finishing ITM — A 0.30 delta roughly equates to a 30% chance of expiring in the money
Calls have positive delta (0 to +1); puts have negative delta (0 to −1).
Gamma (Γ)
Gamma measures how fast delta changes as the stock moves. It's highest for at-the-money options near expiration — a small move in the stock causes a big swing in delta. High gamma means high risk and reward; sellers face "gamma risk" where short options can rapidly become ITM.
Theta (Θ)
Theta measures time decay — how much value an option loses each day, all else equal. Buyers fight theta; sellers collect it. Theta accelerates as expiration approaches, with out-of-the-money options decaying fastest in the final weeks.
Vega (ν)
Vega measures sensitivity to implied volatility — the market's expectation of future price swings. Higher IV helps buyers and hurts sellers; lower IV does the opposite. A volatility crush after earnings is vega working against option buyers.
How Greeks Work Together
Every option position is a mix of these forces. A long call, for example, has positive delta (profits as stock rises), positive gamma (delta grows as the stock moves in your favor), negative theta (loses value each day), and positive vega (gains if implied volatility rises). Successful traders manage the net Greeks of a portfolio.
For Beginners
- Focus on delta and theta first — they explain most moves
- Use your broker's Greeks display before every trade
- Avoid holding long options into the final week (theta spikes)
The Takeaway
The Greeks translate options from mystery to math. Once you can read delta, gamma, theta, and vega, you understand not just whether your trade will profit, but why and how fast. Learn them gradually, check them on every trade, and the Greeks become your most reliable risk-management tool.