Caffeine Half Life Calculator
Instantly estimate how much caffeine is still in your system, when it fully clears, and roughly when it’s safe to sleep, based on your dose and timing.
Calculate Your Caffeine Half Life
Enter your caffeine dose and timing below to get an instant estimate of how much caffeine remains in your system right now, and how long until it’s fully out.
Caffeine Clearance Estimator
Fill in your dose and timing details to see your elimination breakdown
e.g. 95mg brewed coffee, 40mg tea
Time passed since your last dose
Average is 5-6 hrs; pregnancy and some medications roughly double it
Caffeine Remaining
Breakdown based on first-order exponential decay
Caffeine Half Life FAQ
Everything you need to know about how caffeine is metabolized, cleared, and how it affects your sleep.
The average half life of caffeine is about 5 to 6 hours in a healthy adult, meaning half of the caffeine you consume is metabolized in that time. It can range from as little as 2 hours to over 9 hours depending on genetics, liver function, pregnancy, smoking, and certain medications.
It generally takes about 5 half-lives for a substance to be considered fully cleared from the body, which for caffeine works out to roughly 24 to 30 hours based on an average 5 to 6 hour half life. Trace amounts can still be detectable in blood or urine after that point.
Caffeine clearance follows first-order exponential decay. Remaining caffeine equals the original dose multiplied by one-half raised to the power of elapsed hours divided by the half life. This means the amount remaining halves at every interval equal to the half life, rather than dropping by a fixed amount.
Liver enzyme activity, genetics, pregnancy, smoking status, certain medications, and even other foods can all speed up or slow down caffeine metabolism. Smokers tend to clear caffeine faster, while pregnancy and some contraceptive or antibiotic medications can roughly double the half life.