Which Greek matters most?

It depends on the trade. Delta drives most short-term price changes, theta dominates near expiry, and vega matters around events when IV can move sharply.

Why did my call lose money when the stock went up?

Time decay (theta) and a fall in implied volatility (vega) can outweigh a small favourable move, especially close to expiry.

Are Greeks the same on every platform?

Not exactly. They come from a pricing model and an IV estimate, so small differences between platforms are normal.

Do Greeks matter at expiry?

At expiry an option is worth only its intrinsic value, so the Greeks no longer apply. The payoff depends only on the final price.

Option Greeks explained

Updated 11 October 2026

Option payoff calculator →

An option's price moves for more than one reason. The stock moves, time passes, and the market's expectation of volatility changes. The Greeks are numbers that estimate how much the premium changes for each of these. Most option chains and trading apps show them next to each strike.

The Greeks come from a pricing model, usually Black-Scholes or a variant. They are estimates for small changes and they themselves keep changing. Think of them as a dashboard, not a guarantee.

Delta: sensitivity to price

Delta estimates how much the option premium changes for a ₹1 move in the underlying. Call deltas run from 0 to 1, put deltas from 0 to −1. An at-the-money option is usually near 0.5 (or −0.5). Deep in-the-money options move almost one-for-one with the stock; far out-of-the-money options barely move.

Delta is also used as a rough position size. If you hold one call with delta 0.5 on a contract of 500 shares, your position behaves a bit like holding 250 shares, for now.

Gamma: how fast delta changes

Gamma is the change in delta for a ₹1 move in the underlying. It is highest for at-the-money options close to expiry. High gamma means your delta, and so your risk, can change very quickly. This is why short-dated options can swing so violently in the last few days or hours.

Theta: time decay

Theta estimates how much premium is lost per day if nothing else changes. It is usually shown as a negative number for option buyers. Time value does not fade evenly; it tends to drain faster as expiry approaches. Option sellers collect this decay, but they take on the risk of large moves in return.

Vega: sensitivity to volatility

Vega is the change in premium for a one percentage point change in implied volatility (IV). If IV rises from 15% to 16% and vega is 0.80, the premium rises by about ₹0.80. IV often climbs before results or policy announcements and drops after them, which can hurt option buyers even when they guessed the direction right. See how to read an option chain for where IV appears.

Rho: sensitivity to interest rates

Rho measures the change in premium for a one percentage point change in interest rates. For short-dated options it is usually small, so most traders glance at it and move on.

Worked example

Say Stock ABC trades at ₹1,000. You look at the 1000 call with these made-up values:

Item	Value
Premium	₹20.00
Delta	0.50
Gamma	0.004
Theta	−1.50 per day
Vega	0.80 per 1% IV

Step 1, price move. The stock rises ₹10. Using delta alone, the premium rises about 0.50 × 10 = ₹5. Gamma adds a small correction: ½ × 0.004 × 10 × 10 = ₹0.20. Estimated premium: 20 + 5 + 0.20 = ₹25.20. Delta has also grown to about 0.50 + (0.004 × 10) = 0.54.

Step 2, one day passes. Theta takes away ₹1.50, so ₹25.20 − ₹1.50 = ₹23.70.

Step 3, IV falls 2 points. Vega takes away 0.80 × 2 = ₹1.60, so ₹23.70 − ₹1.60 = ₹22.10.

The stock went up ₹10, yet the call gained only ₹2.10, because time decay and the fall in IV ate most of the move. On a made-up lot of 500 shares, that is ₹2.10 × 500 = ₹1,050 instead of the ₹2,600 the first step alone suggested (₹5.20 × 500). Had the stock moved only ₹4, the same day of decay and IV drop could have left the call showing a loss.

How the Greeks fit together

Buyers usually have positive delta (calls) or negative delta (puts), positive gamma, positive vega and negative theta. They need movement, and soon.
Sellers have the opposite: they earn theta but carry negative gamma and vega. A sharp move or an IV spike can cause losses many times the premium collected.
Greeks of a multi-leg position are the sum of each leg's Greeks, which is how spreads reduce some risks while keeping others.

To see the whole picture at expiry, where Greeks no longer matter and only the final price does, use the option payoff calculator.

Limits and honest caveats

Greeks depend on the model and on the IV fed into it, so two platforms can show slightly different numbers. They are accurate only for small moves over short periods; a big gap overnight can make them meaningless. And they say nothing about where the price will go.

SEBI's studies (2023 and 2025) found that about 9 in 10 individual F&O traders lost money in the years studied (SEBI). Understanding the Greeks helps you see why a trade made or lost money. It does not change those odds. Size every position with your worst case in mind, and know your contract size from the lot size guide.

Questions people ask

Which Greek matters most?: It depends on the trade. Delta drives most short-term price changes, theta dominates near expiry, and vega matters around events when IV can move sharply.
Why did my call lose money when the stock went up?: Time decay (theta) and a fall in implied volatility (vega) can outweigh a small favourable move, especially close to expiry.
Are Greeks the same on every platform?: Not exactly. They come from a pricing model and an IV estimate, so small differences between platforms are normal.
Do Greeks matter at expiry?: At expiry an option is worth only its intrinsic value, so the Greeks no longer apply. The payoff depends only on the final price.