Caffeine Limit Calculator
Find your safe daily caffeine limit from bodyweight, capped at the FDA’s 400 mg, with rough coffee and energy-drink equivalents.
How it works
safe daily limit = min(6 mg × bodyweight(kg), 400 mg)
Research on healthy adults points to about 6 mg of caffeine per kilogram of bodyweight as a reasonable daily ceiling, but the effect does not keep scaling for heavier people, so the US FDA caps a generally safe intake at 400 mg a day — very roughly four cups of coffee. This tool takes the lower of your weight-based figure and that 400 mg cap, then translates it into cups and energy drinks using typical caffeine amounts.
Worked example
A 70 kg adult works out to 6 × 70 = 420 mg, which the 400 mg cap trims to 400 mg — about 4.2 cups of coffee or 5 energy drinks spread across the day.
Frequently asked questions
Is 400 mg really safe for everyone?
It is a guideline for healthy adults, not a target. People who are pregnant, sensitive to caffeine, on certain medications, or managing anxiety or heart conditions should aim much lower — often 200 mg or less — and talk to a doctor.
How much caffeine is in my coffee?
An 8 oz brewed coffee averages about 95 mg, but it ranges widely with bean, roast, grind and brew strength. A large café coffee can hold 200 mg or more, so read labels when you can.
What are the signs I have had too much?
Jitteriness, a racing heart, trouble sleeping, headaches and an upset stomach are common flags. Cutting back and avoiding caffeine later in the day usually helps; persistent symptoms are worth a medical check.
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Educational estimate, not medical advice. Consult a qualified professional for health decisions.