Implied volatility calculator

Solve IV from any option's price

Published July 20, 2026

Implied volatility (IV) is the one input to an option's price you cannot read off a screen directly. It has to be backed out of the price. An implied volatility calculator does exactly that: you enter the option's current market price, along with the stock price, strike, days to expiry, and rate, and it solves for the volatility that makes the Black-Scholes model reproduce that price.

How to find implied volatility from a price

You do not calculate IV with a formula the way you calculate a price. Price is a function of volatility, not the other way around, so there is no clean equation that hands you IV directly. Instead a solver searches: it tries a volatility, prices the option, compares the result to the market price, and narrows in until the two match. OptionWit does this by bisection against the same Black-Scholes engine the rest of the site uses, so the number it returns is the exact IV consistent with the price you entered.

To use it, enter the stock price, the strike, the days to expiry, and the option's market price (the mid between bid and ask is best), then press Solve for IV. You can also load a worked example and click Solve to watch it work.

What implied volatility actually is

Implied volatility is the market's estimate of how much a stock will move, stated as an annual percentage and expressed through the option's price. It is "implied" because it is inferred from what people are paying, not measured from the stock itself. A higher IV means the market is paying up for movement, which makes every option on that stock more expensive.

The key thing to hold onto is that IV is derived from price. That is why solving from the price you actually see beats copying a number off a chain, and it is why the same option can carry different IVs in different places.

Why two brokers show different IVs for the same option

Here is the part that trips people up. You can look at the same option, at the same price, on two platforms, and see two different implied volatilities. Neither is broken. They are using different clocks.

Implied volatility depends on time to expiry, and vendors do not all count time the same way. Some count calendar days. Some count trading days. Some adjust for the weekend or for hours. Feed the same price into the model with a different time assumption and you get a different IV, each one internally correct.

An example. Say a put is trading at $3.06 over a weekend, with the stock at $749.30 and a $749 strike. Solve for its implied volatility under three common time conventions:

Solved with the Black-Scholes model at a 4.5% risk-free rate. Same math the calculator runs.

Same option, same $3.06 price, three different answers. The vendor counting the fewest units of time, one trading day over the weekend, reports the highest IV, because it is attributing the option's price to the least time. None of these is wrong. They are answers to slightly different questions.

This is the practical reason to solve IV from the price yourself: the price is the one thing every source agrees on. Once you pick the convention you want (OptionWit lets you switch between calendar and trading days in the advanced inputs), the IV follows from it directly, instead of inheriting whatever clock a particular chain happens to use.

Reading IV off your broker's chain

If you would rather read implied volatility straight from your broker's option chain, the column is there, but it is labeled and placed differently on every platform. Our guide to finding IV on Robinhood, Schwab and thinkorswim, Fidelity, Interactive Brokers, and Webull walks through where each one keeps it. Just remember the number you read carries that platform's time convention, which is why two chains can disagree.

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