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.