Caffeine Half-Life Calculator

Estimate how much caffeine may still be in your system after a certain number of hours.

Example: coffee often ranges from 80 to 200 mg.
Use the time since your last caffeinated drink.
Caffeine half-life varies by person and situation.
How we calculate

We use the half-life formula: remaining caffeine = initial amount × 0.5^(hours ÷ half-life). This gives a rough estimate of how much caffeine may still be active in your system.