Implied Volatility
Implied volatility (IV) is the market's forecast for how much a stock will move. Learn what high and low IV mean, why it sets option prices, and how traders read it.
Implied volatility, or IV, is the market's forecast for how much a stock is likely to move in the future. It does not tell you which direction. It only tells you how big the expected swings are.
High IV means the market expects a wild ride. Low IV means it expects calm. And that forecast is baked directly into the price of every option. Let me explain with the thing IV most resembles: a weather forecast.
The Weather Forecast
A forecast does not tell you it will rain at 3pm on your street. It tells you there is a 70% chance of a storm, so pack accordingly. Implied volatility is the same kind of forecast for a stock. It says, in effect, "expect big moves" or "expect a quiet week," without promising the direction.
And just like umbrellas cost more when a storm is coming, options cost more when IV is high. The market is charging a premium for the expected turbulence. When the forecast is calm, options are cheap.
Where the Forecast Comes From
Here is the clever part. Nobody sits down and declares the IV. It is reverse-engineered from what people are actually paying for options right now.
If traders are paying fat prices for options, the math works backward to say, "for these prices to make sense, the market must expect big moves," and IV reads high. If options are cheap, IV reads low. So IV is not a prediction handed down by an expert. It is the collective bet of everyone trading the options, translated into a single number.
That is also why IV spikes before big events like earnings. Everyone knows a surprise is coming, they bid up options for protection and speculation, and the forecast climbs.
How Traders Use It
The trick is that IV tends to be mean-reverting: it spikes, then drifts back to normal. That gives a simple framework.
When IV is high, options are expensive, so it is a better time to be a seller. You collect the fat premium and profit as the forecast calms down and prices deflate.
When IV is low, options are cheap, so it is a better time to be a buyer. You pay little for the storm premium and hope the forecast climbs.
The question a pro asks is never just "will the stock move?" It is "is the option cheap or expensive relative to how much this stock usually moves?" IV is how they answer that.
- IV is the market's forecast for how much a stock will move, not the direction.
- High IV means expensive options; low IV means cheap options.
- It is reverse-engineered from what traders actually pay for options.
- IV tends to revert to normal, so sell it high and buy it low.
Pop Quiz
Three quick questions to see what stuck. Pick an answer and the explanation shows up right away.
What does implied volatility tell you?
IV is a forecast of the size of expected moves. It says nothing about direction, only magnitude.
IV is high. What does that mean for option prices?
High IV means the market expects big moves, so it charges a bigger premium. Options get pricier.
Since IV tends to revert to normal, when is it generally better to sell options?
Sell when IV is high to collect a fat premium, then profit as the forecast calms and prices deflate.
Bottom Line
Implied volatility is the market's weather forecast, priced right into your options. High IV means expensive options and expected turbulence. Low IV means cheap options and expected calm. It never tells you direction, only the size of the move the crowd is bracing for.
Learn to ask whether an option is cheap or expensive relative to normal, and IV stops being jargon and becomes one of the most useful reads you have.
Keep going: compare the forecast to the past with historical volatility, and watch IV collapse after earnings in IV crush.