IV Rank and IV Percentile - Is Implied Volatility High or Low?

Reviewed by Leon Moyer - Published October 9, 2026 - Last reviewed October 9, 2026

IV rank and IV percentile measure whether a stock's implied volatility is high or low compared with its own past year. IV rank places today's implied volatility between the year's low and high; IV percentile gives the share of days in the year when it was lower than it is today.

What Is Implied Volatility? warned that a raw implied volatility figure means little on its own. A 40% IV is high for a steady utility and low for a volatile small company. IV rank and IV percentile put that figure in historical context by comparing each stock with itself.

Why is raw implied volatility not enough?

Every stock has its own normal range. A large, stable company might spend most of the year between 15% and 25% implied volatility, while a young biotech might rarely drop below 60%. Saying "IV is 40%" does not tell you whether that stock's options are expensive or cheap right now.

The useful question is relative: is implied volatility high or low for this stock? Since higher implied volatility means higher premiums, the answer gives context for premiums with other inputs held fixed. It does not establish fair value: today's event risk and future realized volatility may differ from last year's.

What is IV rank?

IV rank shows where today's implied volatility falls within its range over the past 52 weeks, on a scale from 0 (at the year's low) to 100 (at the year's high).

In one sentence: IV rank = (today's IV - 52-week low IV) / (52-week high IV - 52-week low IV) x 100. The OIC describes IV rank the same way, against the 52-week high-low range; platforms can differ in the details.

What does that mean for prices? With XYZ at $50, a 30-day 50 call costs $1.24 at the year's 20% low, $2.09 at today's 35% and $3.51 at the 60% high (Black-Scholes values with a 4.5% interest rate and no dividends). Holding all other inputs fixed, the model premium is nearly three times as large at 60% IV as at 20%. These are hypothetical repricings, not historical quotes for a contract whose time to expiration changes.

What is IV percentile?

IV percentile looks at every trading day in the past year and counts how many had lower implied volatility than today.

In one sentence: IV percentile = the number of trading days in the past year with IV below today's level / the total number of trading days x 100.

In the XYZ example, suppose implied volatility was below 35% on 189 of the last 252 trading days. The IV percentile is 189 / 252 x 100 = 75. Implied volatility has been lower than today on three days out of four.

So for the same stock on the same day, IV rank says 37.5 and IV percentile says 75. They are answering different questions.

IV rank vs IV percentile: why can they disagree?

IV rank uses only two numbers from the year, the high and the low, so a single extreme day can stretch the range and drag the rank down. IV percentile uses every day, so one spike barely changes it.

Use the same IV measure and lookback for both calculations; a platform may use a constant-maturity composite rather than one contract. Check its treatment of ties and whether today is included in the range. If the high equals the low, IV rank is undefined because its denominator is zero. The OIC introduces these comparisons in Volatility: IV Metrics.

A good habit is to check both. When they agree, the picture is clear. When they disagree sharply, look at a chart of implied volatility over the year to see what happened.

How do traders use IV rank and IV percentile?

These numbers do not predict where a stock is going. They describe where a chosen IV measure sits relative to its history, which feeds into a choice of strategy.

• High IV rank or percentile: the chosen IV measure is high relative to its own history. Holding other inputs fixed, higher IV raises model premiums. That does not establish whether selling compensates for upcoming risk. Buyers face a larger drop if IV falls, as IV Crush showed.
• Low IV rank or percentile: the chosen IV measure is low relative to its own history. Holding other inputs fixed, lower IV reduces model premiums. It does not establish that buying is a bargain; future movement and event risk may differ from the past year.
• Always ask why. Implied volatility is often high for a reason, such as an upcoming earnings report or real trouble at the company. A high reading is a question to investigate, not an automatic trade.