IV rank and IV percentile
IV rank places current implied volatility within its range over a lookback, usually a year: (current − low) / (high − low). IV percentile gives the share of days in the lookback when implied volatility was below the current level. The two can differ widely, because one spike widens the range without changing how often volatility was lower.
Senzoukria · Glossary · Updated September 2026
At a glance
- IV rank
- (IV now − IV low) / (IV high − IV low) × 100
- IV percentile
- % of lookback days with IV below IV now
- Typical lookback
- One year (about 252 trading days)
Two formulas
Both measures express where current implied volatility stands relative to its own history, so that a 20% reading can be judged high or low for that underlying. IV rank uses only the extremes of the lookback: it is 0 at the low and 100 at the high. IV percentile uses the whole distribution: it counts how many observations were below today's level. Neither uses realized volatility; both compare implied volatility with itself.
Worked example
Over the last year, an index's 30-day implied volatility ranged from 12% to 36%, the high coming from a brief sell-off, and was below 20% on 190 of 252 days. With implied volatility at 20% today, IV rank = (20 − 12)/(36 − 12) = 33%, while IV percentile = 190/252 = 75%. The rank suggests volatility is low, the percentile that it is higher than on three days out of four. The single spike to 36% explains the gap.
| Measure | Calculation | Result |
|---|---|---|
| IV rank | (20 − 12) / (36 − 12) | 33% |
| IV percentile | 190 / 252 days below 20% | 75% |
Choices that change the answer
- Which implied volatility: at-the-money of a fixed expiry, a constant-maturity interpolation, or an index such as the VIX.
- Lookback length: a year that includes a crisis gives a low rank for months afterwards.
- Sampling: daily closes versus intraday observations.
- A high rank or percentile says implied volatility is high relative to its past, not that it will fall; high volatility tends to persist for a while.
In Senzoukria
Senzoukria does not compute IV rank or IV percentile, because it does not hold a year of implied volatility history. The 25-delta skew history on its Volatility page ranks the current value only against the points recorded in the current session, at least six of them, and states that this is the session, not a historical percentile. That distinction is deliberate: a percentile over a dozen intraday points is not comparable to one over a year.
Related
In the same section
- Kelly criterion
- Isolated vs cross margin
- Keychain credentials
- Iron condor
- Kill switch
- Introducing broker
- Kyle's lambda
- Intrinsic value
This page in other languages
Frequently asked questions
- Which is better, IV rank or IV percentile?
- Percentile is more robust to single spikes because it uses every observation; rank is simpler and reacts to the range. Reading both, with the lookback stated, avoids the misleading cases.
- Does a high IV rank mean options are overpriced?
- No. It means implied volatility is high relative to its own recent range. Whether options are expensive depends on the volatility that will actually be realized, which the rank does not know.