Caffeine cut-off calculator
Add your drinks and bedtime. You'll see roughly how much caffeine may remain when you go to bed, and the latest times the research suggests for different doses. It's an estimate with stated assumptions, not a measurement.
Left in your system at bedtime
– mg
Likely range –, depending on how quickly you clear caffeine
Research-based cut-offs for your bedtime
- Standard coffee (≈107 mg)–
- Large dose, e.g. pre-workout (≈217 mg)–
From a meta-analysis of 24 studies: finish coffee 8.8 hours, and a pre-workout serving 13.2 hours, before bed to avoid losing total sleep. A later trial found 100 mg had no measurable effect in young men even 4 hours before bed.
How this works, and its limits
The estimate uses a simple pharmacokinetic model: each dose is absorbed over the first hour or so, then eliminated at a constant rate. The central figure assumes a 5-hour half-life, and the range spans 3 to 7 hours. Typical half-lives are often quoted at 3 to 6 hours, and one study found about 7.9 hours in women using oestrogen-containing contraceptives. Smoking speeds clearance; hormonal factors, liver disease and some medicines can slow it considerably.
Cut-off times come from Gardiner and colleagues' 2023 meta-analysis. We apply the coffee figure to doses up to 150 mg and the pre-workout figure above that, which is our simplification.
What this can't tell you: how sensitive you are. Genes, age and habits change how much a given amount of caffeine affects sleep, and people often don't notice the effects. This tool is for planning and curiosity. It isn't medical advice and it can't diagnose a sleep problem. Your entries stay in your browser and are not sent anywhere.
The full evidence is in Caffeine and sleep: how late is too late?