Vega — the fear gauge inside your option

The definition

Vega = how many rupees the option gains when implied volatility rises by 1 percentage point.

The ATM 22400 CE (7 days) has vega ≈ 12.3. If IV goes from 13% to 14%, the call gains about ₹12.3 — with NIFTY not moving at all.

Here's the same call at different volatility levels:

From 13% to 16% (+3 points), the premium rises by ₹37 — about 3 × 12.3. Volatility alone moved the price by more than 20%.

Why volatility moves premiums

Remember the bell curve from the last lesson. Higher volatility = a wider bell. A wider bell means far-away strikes are more reachable, so the option's chance of paying off is higher, so it costs more. Both calls and puts get more expensive when IV rises.

Vega is bigger when there's more time

A change in volatility matters more when there's lots of time for it to play out. Monthly options are far more sensitive to IV than weekly ones on their last day.

The trap: IV crush

Volatility usually rises before a known event (election results, RBI policy, the Union Budget, a company's quarterly results) — nobody knows what's coming. The moment the news is out, uncertainty disappears and IV collapses. Traders call this IV crush.

Watch what it does to a buyer who gets the direction right:

1. 1

   Day before the event

   NIFTY 22,400, IV elevated at 20%. You buy the 22400 CE (7 days) for ₹261.55.

2. 2

   Event happens, NIFTY rises 100 points

   You were right! NIFTY is at 22,500.

3. 3

   But IV crushes back to 13%

   With 6 days left, the call is now worth about ₹219.25.

4. 4

   Result

   You LOSE about ₹42 per unit (≈ ₹2,750 per lot) despite calling the direction correctly.

The delta gain (+100 points × ~0.55) was swamped by the vega loss (−7 IV points × ~12) plus a day of theta.