Implied volatility on its own (say, “IV is 42%”) doesn’t tell you much — is that high or low for this stock? IV rank and IV percentile both answer that by putting current IV in the context of its own past year. They’re the standard gauges traders use to decide whether to lean toward buying or selling volatility.
IV rank
IV rank asks: where does today’s IV sit between its 1-year low and high?
IV rank = (current IV − 52w low) ÷ (52w high − 52w low) × 100
If IV ranged from 20% to 60% this year and it’s 40% today, IV rank is 50%. Simple — but it only looks at the two extremes, so a single volatility spike can stretch the range and push rank artificially low for the rest of the year.
IV percentile
IV percentile asks: on how many days this year was IV lower than today?
IV percentile = (# days IV < current IV) ÷ trading days × 100
If IV has been below today’s level on 80% of days, IV percentile is 80%. Because it counts every day, it reflects how typical the current level is — not just where the extremes were.
Why they disagree
| Metric | What it uses | Weakness |
|---|---|---|
| IV rank | Only the 1-year high & low | One spike skews it for months |
| IV percentile | Every trading day | Slower to react to fresh regime changes |
The two diverge most after a single large, brief IV spike (e.g. a one-off crisis). Rank will read low because the high is far away; percentile will read higher because IV is still above most ordinary days. When they disagree, percentile is usually the more honest read of “how expensive are options, normally.”
How to use them around earnings
- High IV rank/percentile → options are relatively expensive → lean toward selling premium (defined-risk).
- Low IV rank/percentile → options are relatively cheap → buying volatility may be more attractive.
- But for earnings specifically, the more important comparison is the implied move vs the stock’s history of actual moves — that’s what tells you if the event premium is mispriced.
Frequently asked questions
What is IV rank?
IV rank measures where current implied volatility sits between its lowest and highest values over the past year. It is calculated as (current IV − 1-year low) ÷ (1-year high − 1-year low), expressed as a percentage. An IV rank of 100% means IV is at its yearly high.
What is IV percentile?
IV percentile is the percentage of trading days over the past year on which implied volatility was lower than it is today. An IV percentile of 80% means IV was lower than its current level on 80% of days in the past year.
Why do IV rank and IV percentile differ?
IV rank only looks at the high and low extremes, so a single volatility spike can skew it. IV percentile counts every day, so it better reflects how often IV has actually been at a given level. They diverge most when there was one large, brief IV spike during the year.