Caffeine Half-Life Calculator
Track how caffeine moves through your system throughout the day. Caffeine has an average half-life of 5 hours, meaning half is eliminated every 5 hours.
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Caffeine at Bedtime (10:00 PM)
14mg
Minimal - close to optimal for sleep
Caffeine Near Zero
10:00 PM
When caffeine drops below 20mg
Caffeine Levels Throughout the Day
What Sleep Research Actually Shows
Target 0mg at bedtime. Sleep researchers like Matthew Walker recommend having zero caffeine in your system at bedtime. Even 50mg—often cited as a "safe" threshold—is actually the level where EEG studies show measurable sleep disruption begins.
Tolerance doesn't protect your sleep. High-tolerance coffee drinkers may feel fine, but EEG scans show their deep sleep is still reduced. You don't feel the sleep loss because tolerance masks the subjective effects—but your brain's restorative sleep is compromised.
Stop caffeine 10+ hours before bed. With a 5-hour half-life, 200mg at 2pm still leaves ~50mg at 8pm and ~25mg at 2am. Slow metabolizers (half-life 8-10 hours) should stop even earlier.
Based on research from Drake et al. (2013) and sleep scientists at Berkeley, Stanford, and the NIH.