Vega: Implied Volatility & Event-Driven Pricing

Imagine one umbrella at three prices. On a clear day it costs ₹250. When dark clouds gather, sellers ask ₹350. The umbrella has not changed. The fear of rain has. In options, the umbrella is the premium and the fear of rain is implied volatility.

Now the numbers. Take a NIFTY call at 24,500 (the strike is the fixed price in the contract) with NIFTY at 24,500 and 7 days to expiry. This is an illustration using a standard pricing model. At IV of 14 per cent the premium is about ₹190. Raise IV to 18 per cent and the premium becomes about ₹244. The gain is ₹54 for 4 points, or ₹13.5 per point. That ₹13.5 is the vega. One lot is 65 units (from the January 2026 series; confirm with NSE), so one IV point is worth about ₹877 on one lot.

This works in both directions. If IV drops from 14 to 11, the same call falls about ₹40, from ₹190 to ₹150, even if NIFTY does not move. So a buyer of an option gains when fear rises and loses when fear falls. A seller of the same option gains when fear falls and loses when fear rises.

Vega is not the same for every option. It is largest for at-the-money options (strike close to the current price) because their whole premium is time value and depends on what might happen. Deep in-the-money options are mostly intrinsic value, so IV changes them very little.

Time matters too. An option with 6 months left has more vega than one with 2 days left, because a lot more can change in 6 months. A weekly option has small vega but large theta. A longer-dated option has larger vega but smaller theta. This is a trade-off, not a free choice: a longer option costs more money upfront.

India VIX is an index that measures the market's expectation of NIFTY volatility over the next 30 days, built from NIFTY option prices. When India VIX rises, at-the-money premiums usually rise. When it falls they usually fall. VIX is a guide to the market's mood, not a forecast of direction.

Before a known event such as company results or an RBI policy day, nobody knows what will happen, so IV rises. Once the news is out, the uncertainty is gone and IV usually falls fast. This fall is called an IV crush. The buyer who bought before the event paid the high price and may face the drop.

A worked example from module 16: a call bought for ₹45 before results. The stock rises 2 per cent. Delta adds about ₹15, but IV falls and removes about ₹24. The call is worth ₹36 the next morning. The buyer was right on direction and still lost ₹9 a share.

But the crush does not always beat the buyer. If the stock moves much more than the market expected, the gain from delta can be larger than the loss from vega, and the buyer can profit. Sellers face the reverse. They keep the premium on a quiet day, but a big gap can cost them more than they collected. So the event is a bet on whether the actual move is bigger or smaller than the price already expects.