How long does caffeine last?
See when it wears off, personalized to you
Medical Disclaimer: This tool provides general educational estimates. Always consult your prescribing physician or healthcare provider before making medication changes or interpreting results from population-based models.
Frequently Asked Questions
Caffeine has a half-life of about 5 hours, meaning it takes ~5 hours for your body to eliminate half the caffeine. A typical cup of coffee (95 mg) takes 10-15 hours to fully clear.
Stop caffeine intake at least 8-10 hours before bedtime. For a 10 PM bedtime, your last cup should be by noon to 2 PM.
The FDA recommends no more than 400 mg per day for healthy adults — roughly 4 cups of brewed coffee.
Yes. Caffeine half-life increases with age. Older adults metabolize caffeine more slowly.
Caffeine lasts longer than most people think. Its 5-hour half-life means 25% is still active after 10 hours.
Sources
- Drake C, Roehrs T, Shambroom J, Roth T. Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. J Clin Sleep Med. 2013;9(11):1195-1200. Link
- Fredholm BB, et al. Actions of caffeine in the brain with special reference to factors that contribute to its widespread use. Pharmacol Rev. 1999;51(1):83-133. Link
- Institute of Medicine. Caffeine in Food and Dietary Supplements: Examining Safety. 2014. Link
- Nehlig A. Interindividual differences in caffeine metabolism and factors driving caffeine consumption. Pharmacol Rev. 2018;70(2):384-411. Link
- U.S. FDA. Spilling the Beans: How Much Caffeine is Too Much? Link
Methodology
This calculator uses the standard pharmacokinetic first-order elimination model for caffeine metabolism: C(t) = C0 × (0.5) ^ (t / t½) where C(t) is the caffeine remaining at time t, C0 is the initial dose, and t½ is the half-life (default: 5 hours for healthy adults).
The 5-hour half-life represents the population average for healthy, non-smoking adults. Individual half-life varies from 1.5 to 9.5 hours depending on genetics (CYP1A2 enzyme activity), age, pregnancy status, oral contraceptive use, liver function, and smoking status. The "safe for sleep" threshold of 25 mg is based on sleep research suggesting minimal sleep disruption below this level.
Caffeine has a half-life of approximately 5 hours in healthy adults. This means if you drink a cup of coffee with 95 mg of caffeine at 2 PM, about 47 mg will remain at 7 PM, and about 24 mg at midnight. Most sleep researchers recommend having less than 25 mg of caffeine in your system at bedtime. The FDA recommends no more than 400 mg of caffeine per day for healthy adults.
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