Implied volatility: what option prices imply
Implied volatility translates an option price into a model input. Learn what it describes, which assumptions it uses and how to compare it.
By OptionsKing. Publisher and editorial methods.
What you will learn
By the end of this lesson, you should be able to:
- Explain the price-to-IV calculation.
- Translate annualized IV into a horizon.
- State the limits of an expected-move range.
Start with the observed option price, then solve for the volatility that reproduces it in a chosen model. That direction matters: IV is inferred from the quote. We will translate the annualized number into approximate moves without treating it as a directional forecast or a guaranteed range.
IV is not a forecast. Nobody at any exchange sat down and estimated that Nike will move 37 percent over the next year. What happened is that buyers and sellers traded a contract to $3.54, somebody ran Black-Scholes backwards, and 37 percent is the volatility input that produces $3.54. Change the price to $3.80 and the IV changes. The number is downstream of the trade, not upstream of it.
The example this whole series runs on
Nike, June 3. Stock at $74.20. Earnings June 26, after the close.
The July 18 expiry is 45 days out. The $74 put is trading at $3.54, and solving that price backwards gives an implied volatility of 37 percent. That is the raw fact. Everything below is translation.
Translation one: what it means per day
Divide the annual number by the square root of the number of trading days in a year, which is 252, so 15.87.
37 / 15.87 = 2.33 percent a day. On a $74.20 stock that is $1.73.
That sentence is worth more than the 37. "Nike moves about a dollar seventy a day, in either direction, on a typical day" is a thing you can hold in your head while you look at a strike three dollars away and ask whether that is really far.
Translation two: what it means by expiry
The square-root calculation gives an approximate one-standard-deviation scale under simplified assumptions. It is not the average absolute move, a price target or a hard boundary. Events and changing volatility can make actual outcomes differ substantially.
Multiply the spot by the IV by the square root of the time remaining in years. For July 18, that is 45/365, so 0.351.
74.20 x 0.37 x 0.351 = $9.64.
So the market is pricing a range of $64.56 to $83.84 by July 18, and expecting the stock to finish inside it about two times in three. One standard deviation, roughly 68 percent, assuming a normal distribution that stock returns do not actually follow.
Now go look at your strike. If you were about to sell the $70 put and thought you had picked something conservative, the market says $70 is well inside the one-sigma range and is charging you accordingly.
Why anyone bothers with the annualized form
Because dollars do not compare. A $2 expected move means something completely different on Nike than on a $9 stock, and comparing option premiums across two tickers in dollars tells you nothing at all.
IV normalizes. Nike at 37 and a utility at 18 is a statement you can act on. Nike's $3.54 put against the utility's $0.90 put is not.
The four conventions that make two screens disagree
You will look at the same contract on two platforms and get two IVs. All four causes are boring and all four are worth knowing.
- Which price got solved. Bid, ask, mid or last trade. On a contract quoting $3.30 bid at $3.80 ask, those four answers span several volatility points. Solve the mid, always, and if the mid feels like a guess then the contract is telling you something.
- Trading days or calendar days. 252 versus 365 changes the daily-move translation by about 22 percent. Neither is wrong. Mixing them inside one comparison is.
- Which strike. There is no single IV for a stock. Every strike carries its own, and on Nike that July 18 chain runs from 44.5 percent at the $65 put down to 33.2 percent at the $84 call. That spread has a name and a reason.
- Which model. Black-Scholes assumes European exercise and no dividends. American equity options are neither. Different platforms patch this differently, and the patch shows up in the third digit.
Compare IVs within one platform. Never across two.
What high IV is actually telling a seller
That the market expects a big move, and that you are being paid more to be wrong about it.
Both halves are load-bearing. High premium is not a gift, it is a quote for insurance on something the market has decided is risky, and the market is frequently right about that. The useful question is never "is this IV high" but "is this IV high relative to what this stock normally does, and is the reason it is elevated something I am comfortable underwriting". The first half of that question has two standard answers and they disagree. The second half has no formula at all.
Check your understanding
Does a 68 percent model range mean the stock cannot leave it?
Show the explanation
No. Even the simplified distribution places about a third of outcomes outside one standard deviation. Real price behavior can differ further, especially around gaps and events.
Common questions
What does 37 percent implied volatility mean?
That the option is priced as though the stock has a 37 percent annualized standard deviation of returns. Practically, about a 2.33 percent move on a typical day, and a one standard deviation range of plus or minus $9.64 over 45 days on a $74.20 stock.
Is implied volatility a prediction of where the stock is going?
It is a model input inferred from a price, not a directional prediction or a guarantee about future moves. It can contain information about priced uncertainty and risk premia without equaling future realized volatility.
Why is implied volatility different at every strike?
Market prices do not generally fit one constant-volatility distribution. Downside equity skew is common, but the shape depends on the underlying, expiry, and conditions.
Should I use 252 or 365 days to annualize?
Use 252 trading days for converting an annual IV into a per-day move, and calendar days over 365 for the time input in a pricing model. The two conventions answer different questions, and the only real error is mixing them inside one comparison.
Sources
Rules and thresholds above were checked against these documents on August 4, 2026. Exchange and broker rules change. Confirm anything you are about to act on with your own broker.
Keep reading
Do the math on your own trade
Every price in this article is an illustrative worked example, not a quote. Read Volatility for the rest of the series, and the disclaimer before you act on any of it. Selling options carries real risk of loss, and the loss can be far larger than the premium you collected.