Holistic Health
Caffeine Clearance Calculator
Enter what you drank and when, and see exactly when caffeine will clear your system, and when it is safe to sleep without it disrupting your rest.
The 5.7-Hour Half-Life
Caffeine is metabolized by the liver enzyme CYP1A2. The average half-life — the time it takes for half of a dose to be eliminated — is approximately 5–6 hours, with this calculator using 5.7 hours as the standard average. This means that a 200mg dose at 2pm will still have approximately 100mg active at 8pm, and approximately 50mg at 1:30am.
The "safe for sleep" threshold used in this calculator is 25mg of remaining caffeine — approximately the amount in a quarter cup of drip coffee. Below this level, most people experience minimal sleep disruption from caffeine alone, though individual sensitivity varies.