IV Rank and IV Percentile

An implied volatility of 30% means little on its own. For a utility stock it might be extremely high; for a small biotech stock it might be unusually low. IV rank and IV percentile put the current implied volatility in context by comparing it with its own history, usually over the past year. Options traders use them to decide whether premium is rich enough to sell or cheap enough to buy.

IV rank#

IV rank shows where current implied volatility sits between its lowest and highest levels over the lookback period.

IV rank = (current IV - 52 week low IV) / (52 week high IV - 52 week low IV) × 100

IV percentile#

IV percentile shows the percentage of days in the lookback period when implied volatility was lower than it is now.

IV percentile = (number of days with IV below current IV / total days) × 100

Worked example#

IV rank vs IV percentile#

Many platforms show both; traders often look at both together.

How traders use them#

These thresholds are conventions, not rules. Implied volatility can stay high or low for long periods, and high readings often come with genuine risks.

Context matters#

• Events: IV rank is often high before earnings because of the event, not because options are mispriced. After earnings, it typically drops sharply. See Volatility Crush and Expansion.
• Regime shifts: if a company's business has changed, last year's range may not be relevant. See Structural Breaks and Regime Changes.
• Compare with realised volatility: a high IV rank alongside high realised volatility may be fair, not expensive. See Historical and Realized Volatility.
• Lookback length: a one year window is standard, but longer windows include more market cycles.

Mean reversion of implied volatility#

Part of the logic is that implied volatility tends to revert towards its long run average: spikes fade and very low levels eventually rise. This tendency is well documented for indices such as the VIX, though the timing is unpredictable. See Mean Reversion and The VIX.

Common mistakes#

• Selling options just because IV rank is high, without checking for events or news.
• Relying on IV rank alone when a single spike distorts it.
• Assuming low IV must rise soon.

Frequently asked questions#

What is IV rank?#

A measure of where current implied volatility sits between its lowest and highest values over the past year, from 0 to 100.

What is the difference between IV rank and IV percentile?#

IV rank uses only the high and low of the range; IV percentile counts how many days implied volatility was below today's level, which makes it less sensitive to spikes.

What is a good IV rank for selling options?#

Many traders prefer readings above about 50, but there is no universal threshold, and high readings often reflect real upcoming risks.

Next, learn about the best known volatility index in The VIX.