Caffeine Half-Life
When Will Coffee Wear Off?
Estimate how much caffeine remains in your system hour by hour — plan bedtime around your intake.
Caffeine Half-Life Calculator
See how much caffeine remains in your system hour by hour, and when it will clear below the threshold that affects sleep.
How Caffeine Decay Works
Caffeine follows first-order elimination kinetics — it decays exponentially, not linearly. This means a fixed percentage (not a fixed amount) is eliminated each hour. The half-life determines how quickly: with a 5-hour half-life, 200mg becomes 100mg at 5h, 50mg at 10h, 25mg at 15h, and so on.
Caffeine and Sleep
Caffeine blocks adenosine receptors, preventing the "sleepy signal" from accumulating. Even when you no longer feel alert, residual caffeine can reduce deep sleep (NREM Stage 3) duration and delay sleep onset. Studies show that caffeine consumed 6 hours before bed can reduce total sleep time by over an hour.
Formula
Common Caffeine Sources
Tips & Limitations
Medical Disclaimer
This calculator provides estimates based on average caffeine metabolism. Individual variation is significant. If you are sensitive to caffeine, pregnant, or taking medications that affect liver enzymes, consult your healthcare provider.