Caffeine Half-Life & Sleep Predictor
Log your coffee, tea, and energy drink intake. Get a precise 24-hour caffeine decay chart, crash window prediction, and optimal bedtime based on your metabolism speed (slow/normal/fast). Science-based, no sign-up needed.
How to use
- 1Add your drinks for today (type, quantity, time consumed)
- 2Select your metabolism speed (Slow / Normal / Fast)
- 3Enter your target bedtime
- 4View the 24-hour caffeine decay chart and safe sleep time prediction
Frequently Asked Questions — Caffeine Half-Life & Sleep Predictor
What is caffeine's half-life?+
Caffeine's average half-life is about 5.7 hours in healthy adults. Slow metabolizers (CYP1A2 slow allele) may take 9–10 hours; fast metabolizers around 2–3 hours. Pregnant women metabolize caffeine significantly slower.
What is a "caffeine crash" and why does it happen?+
Caffeine doesn't actually create energy — it blocks adenosine receptors, the chemical that causes drowsiness. While caffeine is in your bloodstream, adenosine continues to accumulate. When caffeine drops rapidly, adenosine floods all its receptors at once, causing the sudden fatigue known as a crash.
When should I have my last coffee?+
General rule: stop caffeine at least 8–10 hours before bedtime. If you sleep at 11 PM, cut off by 1–3 PM. Slow metabolizers should stop even earlier. This tool calculates your personalized cutoff time based on your metabolism speed.