Free interactive tool
Calculate caffeine by half-life
Enter each dose and choose a half-life to estimate how caffeine declines over time. The results compare three-, five- and seven-hour scenarios so one average does not look more precise than it is.
Caffeine declines by half once per selected half-life: 200 mg becomes about 100 mg after five hours and 50 mg after ten hours in the central example.
- Adjustable half-life from 1 to 12 hours
- Combined timeline for multiple drinks
- Estimated times below 50, 25 and 10 mg
Example: 200 mg with a five-hour half-life
A 200 mg dose is estimated at 100 mg after five hours, 50 mg after ten hours and 25 mg after fifteen hours. With a slower seven-hour half-life, about 74 mg remains after ten hours; with a faster three-hour half-life, about 20 mg remains.
How to use this calculation
- Enter the labelled caffeine amount for every drink.
- Set the time each serving was consumed.
- Choose the half-life you want to model and compare the sensitivity scenarios.
CaffCalc applies exponential half-life decay to each dose, combines the results and shows the estimated amount over time. It is useful for comparing timing choices, not for diagnosing sleep problems or measuring caffeine in your body.