Free interactive tool
Estimate caffeine remaining at bedtime
The effect of an afternoon drink depends on dose, timing, bedtime and clearance. Use your own schedule rather than relying on a single “no coffee after” rule.
The amount left at bedtime depends on both dose and time. An earlier or smaller serving produces a lower mathematical estimate, but the result cannot predict sleep.
- Bedtime-specific estimate
- Per-drink contribution
- Fast and slow metabolism comparison
Example: a 3 PM coffee before an 11 PM bedtime
A representative 95 mg coffee has eight hours to decline. With a five-hour half-life, about 31 mg remains at 11 PM. A 200 mg café drink taken at the same time leaves about 66 mg, showing why dose matters as much as the clock.
How to use this calculation
- Add all caffeine consumed during the day.
- Set your planned bedtime and a realistic half-life range.
- Compare the result with an earlier or smaller final drink.
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.