What Is Implied Volatility (IV)?

Implied volatility is the market's price for uncertainty. It is one of the biggest reasons an option costs what it does, and one of the most misunderstood.

The plain-English definition

Implied volatility (IV) is the level of future volatility that today’s option prices "imply." Option pricing models such as Black-Scholes take several inputs: stock price, strike, time, interest rate and volatility. Every input except volatility can be observed directly. So you can run the model in reverse: start from the option’s market price and solve for the volatility that would produce it. That number is IV.

IV is quoted as an annualized percentage. A stock with an IV of 30% is priced as though its typical one-year move is about ±30%, measured as one standard deviation. Think of it as a market-set expectation, not a forecast you can count on.

Why IV matters for option prices

An option’s price is made of intrinsic value plus extrinsic (time) value. IV drives a large part of that extrinsic value. Higher IV means a wider range of possible outcomes, which makes the option’s potential payoff more valuable, so the premium rises. Lower IV shrinks the premium. The Greek that measures this sensitivity is vega. See how to read the option Greeks.

Converting IV into an expected move

A common approximation for a one-standard-deviation move over a period:

Under the model’s assumptions, the stock finishes within that range about two-thirds of the time. Real markets have fatter tails than the model assumes, so larger moves happen more often than it suggests. Our expected move calculator does this math and also shows the straddle-price method.

Worked example HYPOTHETICAL

What makes IV go up or down

• Scheduled events: earnings, product launches, court rulings and economic data. IV often builds before the event and drops after it.
• Market stress: IV across many stocks tends to rise when markets fall sharply.
• Supply and demand: heavy buying of options pushes IV up, and heavy selling pushes it down.
• Calm periods: IV often drifts lower when prices are steady.

IV also differs by strike and expiration. Far out-of-the-money puts often carry higher IV than calls at the same distance. This pattern is often called "skew."

IV for buyers vs sellers

Buyers of options (long calls, long puts, straddles) have positive vega. Rising IV helps them, and falling IV hurts. When they pay a high IV, they need a larger move to profit.

Sellers (covered calls, cash-secured puts, iron condors) have negative vega. They collect more premium when IV is high, but high IV exists because the market expects bigger moves. A richer premium is payment for taking on more risk, not a free edge.

IV vs historical volatility

Historical (realized) volatility measures how much the stock actually moved over a past window. IV looks forward and comes from option prices. Comparing the two can show whether options look relatively expensive or cheap compared with recent behavior, but past movement doesn’t guarantee future movement.

Reading IV on an option chain

Most brokers show an IV figure for each strike, and often a single summary IV for the stock or for each expiration. A few practical reading tips:

• Compare expirations. If one expiration has noticeably higher IV than the others, there is often a scheduled event before it, such as earnings.
• Compare strikes. IV that rises for lower strikes shows the market paying extra for downside protection. That pattern is common in equities.
• Compare with the stock’s own history. Some platforms show IV rank or IV percentile, which place today’s IV within the stock’s own range over a past period. These readings are relative, and the method varies by platform.
• Mind the spread. On thinly traded options, a wide bid-ask spread can make the displayed IV unreliable, because it’s computed from a mid-price that may not be tradable.

A second example: same move, different IV HYPOTHETICAL

Common mistakes

• Buying options right before earnings without accounting for IV crush.
• Assuming high IV signals a direction. It doesn’t.
• Comparing IV across very different stocks as if it meant the same thing. Each stock has its own normal range.
• Forgetting that the expected-move range is not a boundary. Moves beyond it happen.

Keep learning

Estimate a range with the expected move calculator, then see how that range relates to a trade’s odds in the probability of profit calculator. Look up expected move, vega and more in the glossary.

FAQ

Is high IV good or bad?
Neither. High IV means options are more expensive, which can be helpful for sellers and costly for buyers. It also means the market expects larger moves, and that is risk for both sides.

What is IV crush?
IV crush is a sharp drop in implied volatility after an expected event such as an earnings report. Option prices can fall even when the stock moves, because the uncertainty premium leaves the price.

Does IV predict which direction the stock will move?
No. IV reflects the expected size of moves, not their direction.

How is IV different from historical volatility?
Historical volatility measures how much the stock actually moved in the past. Implied volatility is worked backwards from current option prices and reflects what the market is pricing in for the future.