Find out exactly when caffeine will leave your system. Enter your drinks, body weight, and see your personalized caffeine decay timeline.
This calculator uses the scientifically established caffeine half-life model to estimate how much caffeine remains in your system at any given time. Caffeine is metabolized by the liver enzyme CYP1A2, and its elimination follows an exponential decay pattern based on your individual half-life.
Caffeine half-life is the time it takes for your body to eliminate half of the caffeine in your system. For most healthy adults, this is approximately 5 hours. That means if you consume 200mg of caffeine, after 5 hours approximately 100mg remains, after 10 hours about 50mg, and after 15 hours roughly 25mg.
Caffeine has a half-life of approximately 5-6 hours in healthy adults. This means if you consume 200mg of caffeine at 2pm, about 100mg remains at 7-8pm. It takes roughly 24-48 hours for caffeine to be nearly eliminated from your body.
Most sleep experts recommend stopping caffeine intake 8-10 hours before bedtime. For a 10pm bedtime, your last coffee should be around noon-2pm. Slow metabolizers may need to stop even earlier — up to 12-14 hours before bed.
Genetics (CYP1A2 gene variation), pregnancy (doubled to 10-12h), smoking (halved to ~3h), oral contraceptives (nearly doubled), age (slower in elderly), liver disease, and body weight all significantly affect how quickly your body processes caffeine.
Yes. Studies show that consuming caffeine even 6 hours before bed can reduce sleep quality by over 1 hour. You may not feel wired, but your deep sleep (slow-wave sleep) can be significantly reduced without you realizing it.
The FDA recommends a maximum of 400mg per day for healthy adults (about 4 cups of brewed coffee). Pregnant women should limit to 200mg. Adolescents should not exceed 100mg per day.
The CYP1A2 gene controls caffeine metabolism. People with the "fast" variant process caffeine about twice as quickly. About 50% of the population carries the slow metabolizer variant. Smokers also metabolize caffeine faster due to enzyme induction from tobacco.