Caffeine Intake Calculator

Caffeine is an everyday aid for focus and exercise performance, but too much causes insomnia, palpitations and anxiety. Safe amounts scale with body weight, so this tool calculates your daily and single-dose limit guidelines (based on the European Food Safety Authority’s assessment) and the pre-workout dose range considered effective (per the International Society of Sports Nutrition).

How to use this tool

Just enter your weight. Results show your daily and single-dose guideline limits, the effective pre-exercise range, coffee-cup equivalents, and typical caffeine contents of common drinks. Energy drinks vary hugely (80–300 mg per can) — always check the label.

Pre-workout caffeine

The ISSN position stand (2021) finds 3–6 mg per kg of body weight about 60 minutes before exercise effective for strength, muscular endurance and aerobic performance. Sensitivity varies a lot, so start at the low end if you are new to it. Caffeine late in the day hurts sleep quality — keep it at least 6 hours before bed if you want to protect your sleep cycles.

Tips

Coffee and tea also count toward hydration (see the Water Intake Calculator). For managing rest between sets after your pre-workout coffee, try the Interval Timer.

Half-life and what is still in you

Caffeine has a half-life of roughly four to six hours — the time for the amount in your body to halve. Take 200 mg at 3 pm and about 100 mg remains at 9 pm, with roughly 50 mg still present at 3 am. Studies have found measurably shorter sleep from caffeine taken six hours before bed, so "not right before bedtime" is not a sufficient rule. Counting back eight hours from your intended bedtime is the safer cut-off.

Half-life varies a lot between people

Caffeine is metabolised mainly by the liver enzyme CYP1A2, and its activity varies genetically. Fast metabolisers clear caffeine in around three hours; slow metabolisers can take eight or more. Pregnancy lengthens the half-life substantially — reports of 15 hours or more in the third trimester — and oral contraceptives and some medications also slow clearance. Smoking speeds it up.

Daily limits and typical amounts

The European Food Safety Authority considers up to 400 mg a day and 200 mg in a single dose safe for healthy adults. During pregnancy and breastfeeding, most authorities advise around 200 mg a day, and less for children. For reference, a 150 mL cup of drip coffee holds about 90 mg, an espresso about 60 mg, a cup of green tea about 20 mg, and an energy drink 80–150 mg. If sleep is the concern, use this alongside the sleep cycle calculator.