How to use IV data: Low IV means options premium is cheap relative to recent history — favorable conditions for buying calls or puts. High IV means premium is expensive — avoid buying options, consider selling spreads instead. IV Rank shows where current IV sits in its 1-year range (0 = historically low, 100 = historically high). IV Percentile shows the % of days in the past year where IV was lower than today. Both update daily before market open.