IV Percentile
The percentage of historical days when implied volatility was lower than the current implied volatility.
Explanation
IV Percentile is distribution-based and less sensitive to isolated outliers than simple high-low comparisons. Higher values imply current IV is elevated relative to its recent history, while lower values imply relatively cheap volatility.
Example
IV Percentile of 82 means current IV is higher than on 82% of observed lookback days.