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Option Greeks Explained: Delta, Gamma, Theta & Vega

Updated August 2026 · By PaperBull Editorial Team

Jump to: Delta · Gamma · Theta · Vega · Summary table · Using Greeks in live trading · Common mistakes · FAQ

Option Greeks are mathematical measures of how an option's price reacts to the things that actually move it — the underlying's price, time passing, and volatility. Understanding them matters whether you're buying options or selling them, because they explain why a trade can go right on direction and still lose money.

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, 0 to +1. A CE with Delta 0.5 gains about ₹50 in premium for every 100-point rise in NIFTY.
• Put options have a negative Delta, -1 to 0. A PE with Delta -0.4 gains about ₹40 for every 100-point fall in NIFTY.
• ATM options sit near Delta ±0.5. Deep ITM options approach ±1. Deep OTM options approach 0.
• Delta doubles as a rough probability of expiring in the money. A Delta of 0.3 implies roughly a 30% chance of expiring ITM.

Practical use: want a position that moves almost like NIFTY futures? Buy a deep ITM CE with Delta near 1. Want smaller exposure for less capital? Buy an OTM CE with Delta around 0.2-0.3.

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

• ATM options have the highest Gamma — their Delta can shift fast on small price moves, which is what makes them jumpy near expiry.
• Deep ITM and deep OTM options have low Gamma — their Delta barely moves.
• Gamma rises sharply as expiry nears, especially for ATM strikes — why buying ATM options on expiry day is high-risk: a small adverse move causes fast Delta deterioration.

Practical use: option buyers like high Gamma — a big move compounds Delta in their favour. Option sellers fear it for the same reason — a short position can move against them fast near expiry.

3. Theta (Θ) — Time Decay

• A NIFTY CE with Theta -5 loses about ₹5 in premium every day, even if NIFTY doesn't move at all.
• Theta decay accelerates as expiry nears — barely noticeable 30 days out, sharp in the last 5 days. Full detail in our Theta Decay guide.
• ATM options decay fastest in absolute rupees; OTM options have smaller premiums but lose a higher percentage as expiry nears.
• Theta is the enemy of option buyers and the friend of option sellers — every quiet day benefits the seller.

Practical use: buying options? Give yourself at least 5-7 days to expiry. Selling? Time decay works for you, but you still need a plan for a sharp move against you.

4. Vega (ν) — Sensitivity to Volatility

• A NIFTY CE with Vega 20 gains about ₹20 in premium for every 1% rise in IV — even if NIFTY doesn't move.
• ATM options have the highest Vega; deep OTM and deep ITM have lower Vega.
• IV Crush: before big events (RBI policy, Budget, results), IV rises and inflates premiums. After the event, IV often collapses fast, even if the market moved as expected — the single most common way option buyers lose on a "correct" trade.

Practical use: before a big event, check IV against its recent average. If it's already elevated, buying is risky — the crush can eat your gains. Selling premium (or a defined-risk spread) often makes more sense there.

Summary: Greeks at a Glance

How to Use Greeks in Live Trading

1. Always check Theta before buying. If the daily decay is large relative to your expected premium gain, reconsider the trade.
2. Use Delta to size your position. On 1 lot of NIFTY (65 shares), an option with Delta 0.5 gains roughly ₹1,625 in position value for a 50-point move (0.5 × 50 × 65) — use that math to judge if the trade fits your target.
3. Before events, check Vega and current IV. High IV + high Vega usually means expensive options likely to deflate post-event.
4. Near expiry, respect Gamma risk. ATM options can swing from nearly worthless to highly valuable in minutes on expiry day, and collapse just as fast.

Common Mistakes With Option Greeks

• Buying options right before a known event without checking if IV is already elevated — the IV crush can hurt even a correct directional call.
• Ignoring Theta on far-dated trades and getting surprised by how much value bleeds out in the final week.
• Treating Delta as a fixed number — it changes constantly as the underlying moves and expiry approaches (that's Gamma at work).
• Selling naked options near expiry without respecting Gamma risk — a sharp move can turn a small premium into a large loss fast.

Frequently Asked Questions