What is implied volatility?

An option price depends on the stock price, the strike, the time left, interest rates, dividends and one input nobody can look up: how much the stock will move before expiration. Implied volatility is the value of that input that makes a pricing model match the price the option actually trades at. It is the market's priced expectation of future movement, not a measurement of the past.

IV is quoted as an annualized one-standard-deviation move. An IV of 30% on a $100 stock means the options are pricing a typical one-year range of about ±$30, which shrinks for shorter periods with the square root of time (the formula is further down). It is non-directional: a stock can carry high IV because traders fear a drop or because they expect a jump.

Each strike and expiration has its own IV, and they rarely match. A single IV figure on a quote screen is a summary of some of those options, so check how your platform defines it before comparing numbers across sources.

Implied volatility vs historical volatility

Historical volatility, also called realized or statistical volatility, measures how much the stock actually moved over a past window, usually as the annualized standard deviation of daily price changes. Implied volatility is what option prices say about the future. One looks back; the other is a price on what comes next.

Comparing the two shows what the market is paying for. If a stock has moved at 25% historical volatility over the past month and its options are priced at 45% IV, the market expects something bigger ahead, often a scheduled event such as earnings. Neither number is a signal on its own: IV can stay high for good reasons, and the stock can move more or less than either one suggests.

  • Historical volatility: backward-looking, calculated from past prices, one number for the stock over a chosen window.
  • Implied volatility: forward-looking, read from option prices, different for each strike and expiration.
  • IV well above historical: options are priced for a bigger move than the recent ones, which is common before earnings.
  • IV below historical: options are priced for a calmer stretch than the recent past.

How does implied volatility move option prices?

Higher IV means a higher premium for calls and puts alike, because a wider range of possible outcomes makes the right to buy or sell worth more. The Greek that measures this is vega: the change in the option price for a one-point change in IV. Our options Greeks guide covers it alongside delta and theta.

Hypothetical: a $100 stock and a $100 call with 30 days left. At 30% IV a standard pricing model values the call at about $3.59 per share, with a vega of about 0.11. At 35% IV and the same stock price it is worth about $4.16; at 25% IV, about $3.02. That is roughly $57 per contract either way, from IV alone, without the stock moving a cent.

So buying an option is two bets at once: one on the direction and size of the move, the other on whether IV rises or falls while you hold it. The longer the time to expiration, the larger vega is and the more IV matters.

What are implied volatility rank (IV rank) and IV percentile?

An IV of 40% can be high for a steady large company and low for a small biotech, so the raw number means little on its own. IV rank and IV percentile compare a stock's current IV with its own range over the past year. Platforms may calculate them over different windows, so compare like with like.

  • IV rank = (current IV − 52-week low IV) ÷ (52-week high IV − 52-week low IV) × 100. A rank of 50 means IV sits halfway between its low and high for the year.
  • IV percentile = the share of trading days over the past year when IV was lower than it is now. A percentile of 80 means IV was lower on 80% of those days.
  • Why check both: say IV ranged from 20% to 80% over the year, but only because of one brief spike, and spent most days between 22% and 30%. At 35%, the rank is (35 − 20) ÷ (80 − 20) × 100 = 25, which sounds cheap, while the percentile could be above 80, which says options are expensive compared with a normal day.

Turn your phone sideways to read the drawing. Tap to close.

A hand-drawn line of a stock’s implied volatility over the past year: most days sit between 22% and 30%, one brief spike reaches the 80% high, the low is 20% and IV is now 35%. A side scale shows IV rank = (35 − 20) ÷ (80 − 20) × 100 = 25, which sounds cheap, while the IV percentile could be above 80, expensive next to a normal day.

What is IV crush after earnings?

IV crush is the sharp drop in implied volatility after a known event, most often an earnings report. Before the report nobody knows the numbers, so IV usually climbs in the days leading up to it and options get more expensive. Once the news is out, that uncertainty is gone and IV often falls hard, sometimes by half or more. Option buyers lose the extra premium they paid for the uncertainty, even when the stock moves their way.

Companies usually release earnings before the market opens or after it closes, so the drop shows up at the next open. A report after the 4:00 p.m. ET close lands at 11:00 p.m. in Riyadh until November 1, 2026, and at midnight after US clocks fall back; the reaction then comes at the 9:30 a.m. ET open, 4:30 p.m. Riyadh time (5:30 p.m. from November 1). Earnings season runs four times a year, starting in the first weeks after each quarter ends.

IV crush example: right direction, losing trade

A hypothetical with made-up numbers from a standard pricing model. Stock XYZ trades at $150 on the afternoon before an after-close earnings report. You buy the $155 call expiring in 8 days for $5.90, or $590 per contract, with IV at 90%. Overnight, IV falls to 35%. Had IV stayed at 90%, a $156 open would have left the call worth about $8.30. With the crush, the stock has to rise about 6.4%, to roughly $159.55, just for the call to get back to $5.90.

Here is what the call is worth the next morning, depending on where XYZ opens. The losing cases are shown as plainly as the winning ones, and the right direction alone is not enough:

  • Down 3.3% to $145: about $0.29, a loss of about $561 per contract (−95%).
  • Flat at $150: about $1.13, a loss of about $477 (−81%).
  • Up 4% to $156, above the strike, the “right” way: about $3.60, a loss of about $230 (−39%).
  • Up 6.7% to $160: about $6.26, a gain of about $36 (+6%), close to break-even after a big move your way.
  • Up 10% to $165: about $10.47, a gain of about $457 (+77%).

Turn your phone sideways to read the drawing. Tap to close.

A hand-drawn bar chart of the hypothetical $155 call bought for $5.90 with IV at 90%, valued the next morning after IV falls to 35%, by where XYZ opens: $145 (−3.3%) about $0.29, −$561; flat at $150 about $1.13, −$477; $156 (+4%) about $3.60, −$230 despite the right direction; $160 (+6.7%) about $6.26, +$36; $165 (+10%) about $10.47, +$457. A dashed line marks the $5.90 paid.

What is the VIX?

The VIX, or Cboe Volatility Index, is the best-known gauge of implied volatility for the US stock market as a whole. Cboe calculates it in real time from the prices of S&P 500 index (SPX) options, and it reflects the market's expectation of S&P 500 volatility over the next 30 days, expressed as an annualized figure.

Cboe's own rule of thumb: a VIX of 16 implies an expected annual move of about ±16% for the S&P 500, or roughly ±1% a day. A higher VIX means the market expects bigger swings and is paying more for options; like any IV, it does not say which direction. And it describes the index, not your stock: a single stock's IV can spike on its own news while the VIX stays calm.

If you trade SPX or SPY options, the VIX is a quick read on how expensive 30-day index options are today compared with recent weeks.

How to calculate the expected move from implied volatility

Because IV is annualized, you scale it to your time frame with the square root of time. A common approximation for a one-standard-deviation move by expiration: expected move ≈ stock price × IV × √(days to expiration ÷ 365).

Worked example, hypothetical: a stock at $200, IV of 40%, 30 days to expiration. √(30 ÷ 365) is about 0.287, so the expected move is about $200 × 0.40 × 0.287 ≈ $23. The options are pricing a one-standard-deviation range of roughly $177 to $223 by expiration. For a single day, many traders use the Rule of 16: divide IV by 16, close to the square root of 252 trading days. Here 40% ÷ 16 = 2.5%, about $5 a day on a $200 stock. Keep these limits in mind:

  • It is a size, not a direction. The range runs both ways from the current price.
  • One standard deviation is not a wall. Under the bell-curve assumption, about two outcomes in three land inside it; real markets produce large moves more often than a bell curve suggests.
  • Use calendar days over 365 or trading days over 252, not a mix. The two give close results.
  • Compare it with your plan. If your target needs a much bigger move than the options price in, you are betting on more than the market expects.

Practical rules for option buyers

None of these say what to buy. They are checks that keep IV from surprising you:

  • Check the earnings date before you buy any option. If a report falls before your expiration, you are holding an earnings trade whether you meant to or not.
  • Avoid buying right before earnings unless the event is the trade. If it is, decide in advance how much of the premium you accept losing to IV crush.
  • Compare IV with the stock's own history, using IV rank or IV percentile, not with other stocks.
  • When IV is high versus its history, the stock has to move more for a long option to pay. When it is low, options are cheaper, but low IV can stay low for a long time.
  • Size for the worst case. A long option can lose its whole premium, and a high-IV premium is a bigger amount to lose.
  • Use an options profit calculator for the breakeven at expiration, and remember that it ignores IV changes before then.

Why a chart signal does not account for implied volatility

A chart signal lives on the price chart of the stock or ETF. It can show where a setup is, where the stop belongs and where the target is. It cannot tell you whether the options on that stock are cheap or expensive, because IV is not on the price chart. Two identical breakouts can make a reasonable option trade one week and a poor one the next, purely because IV changed.

That includes our own indicator. UpTickFlow runs on the chart of the underlying and draws an entry, a stop and a target before the trade. It stays quiet when the chart itself shows abnormal volatility, but that is price movement on the chart, not options IV: it does not read options data, so it cannot see IV, IV rank or the expected move, and it does not pick strikes or expirations. Before you turn any signal into an options trade, check the earnings date, the IV and its rank, the expected move against your target and the bid-ask spread on the contract.

The full routine, from chart signal to contract, is in our guide to trading options with TradingView. If you are just starting, read options trading for beginners first, and our guide on how to choose a strike price next.