Caffeine Safe Limit by Body Weight

The FDA recommends a flat 400 mg/day for healthy adults, but sports-nutrition research often scales caffeine by body weight (3–6 mg per kg). See your personalized ceiling below.

What's your personal caffeine limit?
The FDA recommends no more than 400 mg/day for healthy adults, but sports-nutrition research often scales caffeine by body weight (3–6 mg per kg). See your personalized ceiling below.
Your recommended daily ceiling
400mg / day

Based on 70 kg (154.3 lb) at 6 mg/kg, capped at the FDA's 400 mg ceiling for healthy adults.

3 mg/kg (ergogenic)
210 mg
6 mg/kg (high)
420 mg

How many servings is your ceiling?

1 serving = 95 mg24% of ceiling

You could drink about 4 servings of Brewed Coffee before hitting your ceiling.

Disclaimer: The FDA's flat 400 mg/day limit applies regardless of body weight. The body-weight calculation (3–6 mg/kg) is based on sports-nutrition research and may not be appropriate for caffeine-sensitive individuals, those with heart conditions, or pregnant women. Always consult a healthcare provider for personalized guidance.

How the body-weight calculation works

The FDA's 400 mg/day safe limit is a population-level guidance — it's the dose below which most healthy adults don't experience negative health effects. But caffeine's effects depend on how much of it ends up in each kilogram of your body tissue, which means a 50 kg adult and a 100 kg adult will feel very different effects from the same 200 mg dose.

Sports-nutrition research has settled on 3–6 mg of caffeine per kilogram of body weight per day as the typical "ergogenic" (performance-enhancing) range. For a 70 kg adult, that's 210–420 mg per day. The calculator above shows you both ends of this range, capped at the FDA's 400 mg ceiling for safety.

Why we cap at 400 mg

Even though 6 mg/kg for a 90 kg adult would be 540 mg, the FDA has not validated safety above 400 mg/day for the general population. Heavier adults may not experience acute toxicity at 540 mg, but the long-term cardiovascular, sleep, and anxiety effects at that dose have not been studied as thoroughly. We cap the body-weight calculation at 400 mg to stay within FDA-validated safety.

When this calculation does NOT apply

  • Pregnancy: ACOG recommends ≤200 mg/day regardless of body weight
  • Adolescents (12–18): AAP recommends ≤100 mg/day regardless of body weight
  • Children under 12: AAP recommends avoiding caffeine entirely
  • Caffeine-sensitive individuals: CYP1A2 slow metabolizers may need to stay under 200 mg/day regardless of body weight
  • People with anxiety, hypertension, arrhythmia, or GERD: Often need to stay well below 400 mg/day regardless of body weight

Always consult a healthcare provider for personalized guidance on safe caffeine intake for your situation. See our medical disclaimer for details.