Caffeine Per Body Weight Calculator
Scale a safe caffeine dose to your body weight — the 3–6 mg/kg performance range and where the 400 mg daily cap sits for you.
How it works
Performance dose = 3–6 mg/kg body weight · General adult daily cap ≈ 400 mg
Caffeine research on alertness and endurance clusters around 3–6 mg per kg of body weight taken before activity, so a lighter person needs a smaller dose than a heavier one for the same effect. Separately, most health authorities put a general ceiling of about 400 mg per day for healthy adults across all sources. Sensitivity, pregnancy, medication and sleep can all push your personal safe amount well below these figures.
Worked example
A 70 kg adult lands in a 3 × 70 = 210 mg to 6 × 70 = 420 mg performance window. Because the practical daily cap is 400 mg, they would keep a single pre-workout dose toward the lower-to-middle of that range — roughly 210–280 mg, about two cups of coffee.
Frequently asked questions
Is 400 mg a hard limit?
It is a general guideline for healthy, non-pregnant adults, not a personalised safe dose. People sensitive to caffeine, those with heart conditions, and pregnant people should aim much lower — often 200 mg/day or less.
Why scale caffeine to body weight?
A given milligram dose reaches a higher blood concentration in a smaller person. Dosing per kg keeps the effect — and the jitteriness risk — more consistent across body sizes.
Does this include coffee, tea and energy drinks?
Yes. The daily cap is total caffeine from every source combined, including sodas, pre-workout, chocolate and any caffeine pills.
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Educational estimate, not medical advice. Talk to a doctor, pharmacist or registered dietitian before starting or changing any supplement, especially if you are pregnant, nursing, on medication or managing a health condition.