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Caffeine Safe Limit Calculator

Know how much caffeine is safe for you in a day.

How it is calculated

Only body weight in kilograms is used. The daily limit is 5.7 mg × weight, capped at 400 mg: the lower of the two applies, so the weight-based figure is the answer below roughly 70 kg and 400 mg takes over above it. The single dose is 3 mg × weight and has no cap. The coffee figure is daily limit ÷ 95, assuming about 95 mg of caffeine per 8 oz cup of brewed coffee. Values are rounded to whole milligrams and one decimal of cups. Weights below 2 kg or above 650 kg are rejected and show no result. These are rules for healthy adults; the tool does not make allowances for pregnancy, medicines, heart conditions or adolescents, for whom lower limits are usually advised.

Worked example

A person weighing 60 kg. Daily limit = 5.7 × 60 = 342, which is below the 400 mg cap, so the answer is 342 mg per day. Single dose = 3 × 60 = 180 mg. Coffee cups = 342 ÷ 95 = 3.6, shown as 3.6x, about three and a half 8 oz cups spread through the day. A 90 kg person would hit the 400 mg cap, since 5.7 × 90 = 513, while the single dose would still scale up to 270 mg.

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Common mistakes

  • Entering pounds. The field is kilograms, so 154 lb is about 70 and not 154; the wrong unit would give the 400 mg cap and a single dose over twice as high.
  • Treating the daily limit as a target. It is the ceiling for habitual intake, and many people feel effects well below it.
  • Taking the full single-dose figure several times in a day. Single dose and daily limit are separate checks, and the daily total still has to stay under the daily cap.
  • Counting only coffee. The coffee equivalent assumes 95 mg per cup, while energy drinks, tea, cola, pre-workout powders and some pain relievers add caffeine that is not in the cup count.
  • Applying an adult result to a child or adolescent. The single-dose figure grows with weight without any cap, and a heavier adult's 3 mg/kg dose is not a sensible amount to take at once.

Sources

About this calculator

Safe daily caffeine limits are generally set as an absolute ceiling — the US FDA cites roughly 400 mg/day as not typically associated with dangerous effects for most healthy adults — alongside weight-based guidance, since caffeine sensitivity and toxicity risk scale with body mass; European guidance (EFSA) treats single doses up to about 3 mg per kilogram of body weight as safe and habitual daily intake up to about 5.7 mg/kg, with lower thresholds recommended for adolescents.

Physicians, sports nutritionists, and energy-drink and supplement manufacturers reference weight-adjusted caffeine limits because a fixed daily number doesn't account for the wide range of adult body sizes, and because acute overconsumption (rather than typical daily intake) is the greater safety concern — caffeine toxicity symptoms like rapid heartbeat, anxiety, and in rare severe cases cardiac events are dose-dependent and disproportionately affect lighter individuals at the same absolute intake.

Your body weight sets two numbers: an estimated safe daily caffeine limit of 5.7 mg per kilogram (never above 400 mg) and a single-dose limit of 3 mg per kilogram.

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