How implied volatility is calculated
There is no formula that gives IV directly. The calculator tries different volatilities in the Black-Scholes model and narrows down (by bisection) until the model price matches the market price you entered to within a fraction of a paisa.
Worked example
A Nifty 25,000 call trades at ₹194 with 7 days left and Nifty at 25,000. Solving Black-Scholes gives an IV of about 13%. That implies a one-standard-deviation move of about ₹450 by expiry: 25,000 × 13% × √(7/365).
Using IV in your trading
- Compare an option's IV with its own history (IV percentile) to judge whether options are cheap or expensive.
- Sell premium when IV is high relative to history and buy when it is low.
- Expect IV to fall after scheduled events. Buying options just before results often loses money even when the direction is right.
Frequently asked questions
What is implied volatility?
Implied volatility (IV) is the volatility that makes the Black-Scholes price equal the option’s market price. It is the market’s forecast of how much the underlying will move, expressed as an annual percentage.
Why does IV differ between strikes?
This is called the volatility skew. Out-of-the-money puts usually trade at higher IV because traders pay extra for crash protection.
Why does the calculator say no IV exists?
If the option price is below its intrinsic value (or the minimum the model allows), no volatility can produce it. This usually means a stale or illiquid quote, or a wrong spot or strike.
Is high IV good or bad?
High IV makes options expensive — better for sellers, worse for buyers. IV often rises before events like results or the Budget and falls sharply after them (an “IV crush”).
Results are estimates for educational purposes only and are not investment, tax or financial advice. Verify figures with your broker or advisor before acting on them.