How long does caffeine stay in your system?
Caffeine leaves your system gradually. Its half-life is the time needed to eliminate half the dose, rather than all of it. The European Food Safety Authority describes an average of about four hours in healthy adults, with a range of two to eight hours. Your own rate can differ.
That range comes from EFSA’s caffeine explainer. It also describes variation with pregnancy, medicines and other individual factors. A tracker cannot measure those factors just from your drinks.
Half gone does not mean all gone
Suppose a drink contains 100 mg of caffeine and, for this example, your half-life is five hours. A simplified model would leave roughly:
- 50 mg after five hours. Half the original dose remains.
- 25 mg after ten hours. Half of that remaining amount.
- 12.5 mg after fifteen hours. The amount keeps falling.
This is an illustration of exponential decay, not a measurement of your body. It treats absorption as immediate; real absorption takes time.
Several coffees overlap
A second coffee arrives while some caffeine from the first is still present. Counting cups tells you how many drinks you had, but misses their strength and timing. Two small coffees early in the morning can produce a different evening estimate from the same drinks later in the day.
How BeanFade estimates caffeine remaining
BeanFade uses your logged caffeine amounts, drink times and chosen metabolism setting. Free presets use half-lives of 3.5, 5 or 7 hours. Premium lets you choose an exact value between 2 and 12 hours. These are adjustable model settings, not a metabolism test.
The app shows one curve for your drinks, including absorption, and an estimate at bedtime. Drinks you forget to log and inaccurate caffeine amounts affect the result. Coffee strength can vary with beans, serving size and preparation.
Can you use the estimate to plan your last coffee?
You can use it as a planning aid. BeanFade compares the estimate with your chosen sleep line, using your own bedtime and usual drink. Read how the coffee cut-off works for the distinction between a personal threshold and a sleep guarantee.
Source and review
Health information checked against EFSA’s caffeine risk-assessment explainer on 24 October 2026. Written by a developer, not a clinician. For questions about medicines, pregnancy or a health condition, ask a qualified health professional.