Free interactive tool
When might your caffeine level fall?
Feeling less alert does not mean caffeine has fully cleared. Calculate approximate threshold times from all the drinks you consumed and see how each dose changes the combined curve.
Caffeine does not switch off at one exact time. It declines gradually, so this page reports estimated reference levels rather than claiming a precise moment when every effect ends.
- Three clearly labelled reference points
- Accounts for overlapping doses
- Transparent formula and limitations
Example: why “wear off” is gradual
With a five-hour half-life, 100 mg declines to 50 mg after five hours, 25 mg after ten hours and 12.5 mg after fifteen hours. It approaches zero gradually, so CaffCalc reports reference milestones rather than claiming one exact moment when every effect ends.
How to use this calculation
- Enter each dose at the time it was consumed.
- Run the calculation to combine overlapping drinks.
- Read the 50 mg, 25 mg and 10 mg times as estimates—not medical or sleep thresholds.
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.