Caffeine cutoff calculator

Uses the ~8.8 h caffeine-to-sleep gap from the Gardiner meta-analysis on caffeine and sleep. Extra cups add a small conservative buffer so “last sip” moves earlier. Your wake time anchors context for the day; the math is driven by bedtime.

Usual wake timeTypical bedtime (sleep onset)Cups of coffee (today)~95 mg caffeine per cup (brew varies). Tea or energy drinks — convert mentally to “coffee equivalents.”

For 2 cups (~190 mg total if coffee-sized), aim to finish all caffeine by about 13:21 on nights you sleep around 22:30.

That is 9.15 h before lights-out — 8.8 h base (meta-analysis) + 0.35 h for extra cups.

Slow metabolizers, pregnancy, anxiety, and some medications warrant earlier cutoffs. This tool encodes a population prior, not your blood levels.

Educational estimates only. Sleep and caffeine metabolism vary widely. This is not medical advice; talk to a clinician if you have insomnia, apnea, or other conditions.