Option Greeks Explained: Delta, Gamma, Theta & Vega

Updated April 2026 · By PaperBull Editorial Team

Option Greeks are mathematical measures that describe how an option's price changes in response to different factors — underlying price movement, time passing, and volatility shifts. Understanding the Greeks is essential for any serious F&O trader in India, whether you are buying options or selling them.

The four primary Greeks are: Delta, Gamma, Theta, and Vega. Each tells you something different about your option's behaviour.

1. Delta (Δ) — Sensitivity to Price Movement

• Call options have a positive Delta ranging from 0 to +1. If a CE has Delta of 0.5, a 100-point rise in NIFTY increases the option premium by approximately ₹50.
• Put options have a negative Delta ranging from -1 to 0. A PE with Delta of -0.4 gains approximately ₹40 for every 100-point fall in NIFTY.
• ATM options have Delta close to ±0.5. Deep ITM options have Delta close to ±1. Deep OTM options have Delta close to 0.
• Delta is also used as an approximation for the probability that an option will expire in the money. A Delta of 0.3 suggests roughly a 30% chance of expiring ITM.

Practical use: If you want a position that moves almost like the underlying (e.g., NIFTY futures), buy a deep ITM CE with Delta near 1. If you want lower exposure with smaller capital, buy an OTM CE with Delta of 0.2–0.3.

2. Gamma (Γ) — Rate of Change of Delta

• ATM options have the highest Gamma. This means their Delta can change rapidly with small price moves — making them more sensitive near expiry.
• Deep ITM and deep OTM options have low Gamma. Their Delta barely changes with price moves.
• Gamma increases sharply as expiry approaches, especially for ATM options. This is why buying ATM options on expiry day is very high risk — a small adverse move causes rapid Delta deterioration.

Practical use: Option buyers love high Gamma because a big price move can cause Delta to compound. Option sellers fear high Gamma for the same reason — their short position can blow up quickly near expiry on big moves.

3. Theta (Θ) — Time Decay

• If a NIFTY CE has Theta of -5, its premium drops by approximately ₹5 each day — even if NIFTY does not move at all.
• Theta decay accelerates as expiry approaches. An option loses very little time value 30 days before expiry, but loses significant value in the final 5 days.
• ATM options experience the fastest Theta decay in absolute rupee terms. OTM options have smaller premiums but lose a higher percentage of their value as expiry nears.
• Theta is the enemy of option buyers and the friend of option sellers. Every day that passes without a big move benefits the seller.

Practical use: If you are buying options, buy with sufficient time to expiry (at least 5–7 days). Avoid buying ATM options on Monday morning for a Thursday expiry without expecting a big intraday move. If you are selling options, time decay works in your favour — but ensure you have risk management for a sharp move against you.

4. Vega (ν) — Sensitivity to Volatility

• If a NIFTY CE has Vega of 20, its premium increases by ₹20 for every 1% rise in IV — even if NIFTY doesn't move.
• ATM options have the highest Vega. Deep OTM and deep ITM options have lower Vega.
• IV Crush: Before major events (RBI policy, Budget, quarterly results), IV rises sharply — inflating premiums. After the event, IV collapses rapidly even if the market moves in the expected direction, causing option buyers to lose money. This is called IV crush and it is one of the most common pitfalls for retail option buyers.

Practical use: Before a major event, compare IV to its historical average. If IV is already elevated, avoid buying options — the IV crush will eat your profits. Consider selling options instead (straddles or strangles) to capitalise on the expected IV decline after the event.

Summary: Greeks at a Glance

How to Use Greeks in Live Trading

1. Always check Theta before buying options. If time decay is high relative to expected premium gain, reconsider the trade.
2. Use Delta to size your position. If you want a 50-point NIFTY move to earn ₹5,000 profit on a 1-lot position (75 shares), you need a Delta of at least 0.67.
3. Before events, check Vega and current IV levels. High IV + high Vega = expensive options, likely to deflate post-event.
4. Near expiry day, respect Gamma risk. ATM options can move from worthless to highly valuable in minutes on expiry, but can also collapse just as fast.