Caffeine Calculator
Pre-workout dose from your bodyweight (3–6 mg/kg), plus how much would still be in your system at bedtime. Not medical advice.
Methodology
Pre-exercise dose = bodyweight × 3–6 mg/kg (ISSN position stand), taken roughly 30–60 minutes before training, rounded to the nearest 25 mg. If you say you're sensitive, the window drops to 2–3 mg/kg and single doses are bounded by the ~200 mg EFSA single-dose reference. The top of every window is capped at the EFSA healthy-adult daily reference of 400 mg — higher doses add side effects, not performance. The sleep check assumes a ~5 hour half-life: remaining = dose × 0.5^(hours ÷ 5). All caffeine sources count toward the total — coffee (~90 mg per filter cup), tea, cola, energy drinks and pre-workouts.
Sources
- Guest NS et al. ISSN position stand: caffeine and exercise performance. JISSN 2021. PubMed 33388079. link
- EFSA — Scientific Opinion on the safety of caffeine (2015). Single doses up to 200 mg and daily intakes up to 400 mg are not a safety concern for healthy adults. link
- NHS — Foods to avoid in pregnancy: limit caffeine to 200 mg/day. link ACOG — Moderate caffeine consumption during pregnancy: less than 200 mg/day does not appear to be a major contributing factor in miscarriage or preterm birth. link
- Maughan RJ et al. IOC consensus: dietary supplements and the high-performance athlete. BJSM 2018. PubMed 29540367. link
Frequently asked questions
How much caffeine should I take before training? How much caffeine should I take before training?
The ISSN position stand supports about 3–6 mg per kg of bodyweight taken roughly 30–60 minutes before exercise. This tool shows that window for your weight, capped at the 400 mg/day healthy-adult reference point. The ISSN position stand supports about 3–6 mg per kg of bodyweight taken roughly 30–60 minutes before exercise. This tool shows that window for your weight, capped at the 400 mg/day healthy-adult reference point.
Is 400 mg of caffeine a day safe? Is 400 mg of caffeine a day safe?
EFSA concluded daily intakes up to 400 mg, and single doses up to about 200 mg, are not a safety concern for healthy, non-pregnant adults. Individual tolerance varies a lot — this is a reference point, not a target. EFSA concluded daily intakes up to 400 mg, and single doses up to about 200 mg, are not a safety concern for healthy, non-pregnant adults. Individual tolerance varies a lot — this is a reference point, not a target.
How long before bed should I stop having caffeine? How long before bed should I stop having caffeine?
Caffeine has a half-life of about 5 hours, so half of a dose is still in your system 5 hours later. A common rule is to keep meaningful doses at least 6–8 hours away from bedtime; the calculator shows how much of your dose would remain at bed. Caffeine has a half-life of about 5 hours, so half of a dose is still circulating 5 hours later. A common rule is to keep meaningful doses at least 6–8 hours away from bedtime; the calculator shows how much of your dose would remain at bed.
Does coffee count towards the dose? Does coffee count towards the dose?
Yes — all sources count. A filter coffee is roughly 90 mg, an espresso about 80 mg, tea 40–50 mg, and pre-workouts commonly 150–300 mg per serving. Check labels and add everything up. Yes — all sources count. A filter coffee is roughly 90 mg, an espresso about 80 mg, tea 40–50 mg, and pre-workouts commonly 150–300 mg per serving. Check labels and add everything up.
What about caffeine in pregnancy? What about caffeine in pregnancy?
NHS guidance is to limit caffeine to 200 mg/day in pregnancy. This calculator does not personalise performance doses during pregnancy or breastfeeding — speak to your midwife or GP. US guidance commonly cites under 200 mg/day in pregnancy. This calculator does not personalise performance doses during pregnancy or breastfeeding — speak to your OB-GYN or physician.
Is this medical advice? Is this medical advice?
No. It is an educational estimate from published position stands and safety opinions. If you have a heart condition, high blood pressure, anxiety or sleep problems, or take medication, get individual advice first. No. It is an educational estimate from published position stands and safety opinions. If you have a heart condition, high blood pressure, anxiety or sleep problems, or take medication, get individual advice first.