How is the caffeine limit calculated by body weight?

EFSA's per-kilogram figures are used: up to 5.7mg of caffeine per kilogram of body weight per day, and up to 3mg/kg in a single sitting, raise no safety concern for healthy adults. A 70kg adult gets 399mg per day, which is where the familiar 400mg guideline comes from. For adolescents the calculator uses 3mg/kg per day, capped at the AAP's 100mg recommendation.

What are the signs you have exceeded your caffeine limit?

Common signs include jitteriness, a racing or pounding heart, anxiety, upset stomach, headache, and trouble falling asleep. The FDA notes that rapid consumption of around 1,200mg can cause toxic effects like seizures, but problems with sleep and anxiety start far lower for most people.

Do energy drinks count differently from coffee?

Milligram for milligram the caffeine is the same, but energy drinks make limits easier to exceed: a single can ranges from 80mg to 300mg and is often consumed quickly. The AAP says children and teens should avoid energy drinks entirely, and a single high-caffeine can plus a morning coffee can put even a healthy adult over 400mg.

Caffeine Safe Limit Calculator: Your Daily Maximum by Age & Weight

The Guidelines Behind Each Limit

Healthy adults: 400mg per day (FDA)

The U.S. Food and Drug Administration cites 400mg a day, about four or five cups of coffee, as an amount not generally associated with dangerous, negative effects for healthy adults. It is a guideline, not a target: many people sleep and feel better well below it. Source: FDA, Spilling the Beans: How Much Caffeine Is Too Much?

By body weight: 3mg/kg single dose, 5.7mg/kg per day (EFSA)

The European Food Safety Authority works per kilogram instead of a flat number: single doses up to 3mg/kg and habitual daily intake up to 5.7mg/kg (the equivalent of 400mg for a 70kg adult) raise no safety concerns for healthy adults. For a 60kg adult the daily figure works out to roughly 340mg, which is why this calculator lowers the limit when you enter a lower body weight. Source: EFSA Scientific Opinion on the Safety of Caffeine (2015).

Adolescents: at most 100mg per day (AAP)

The American Academy of Pediatrics discourages caffeine for children entirely and, in its clinical report on sports and energy drinks, cites 100mg per day (about one small coffee) as the ceiling for adolescents who do consume it. The AAP also advises that children and teens avoid energy drinks completely. EFSA's per-weight guidance (3mg/kg per day) gives a similar range for typical teen body weights. Source: AAP Clinical Report, Sports Drinks and Energy Drinks for Children and Adolescents (Pediatrics, 2011).

Pregnancy and breastfeeding: 200mg and 300mg

ACOG advises less than 200mg per day during pregnancy, and the CDC notes up to 300mg per day is usually compatible with breastfeeding. If this applies to you, the dedicated pregnancy caffeine calculator tracks drinks against the 200mg guideline with sources. Sources: ACOG Committee Opinion No. 462; CDC, Maternal Diet and Breastfeeding.

Caffeine-sensitive people: there is no official number

Sensitivity varies enormously. Variants of the CYP1A2 gene make some people metabolize caffeine several times slower than others, and slow metabolizers feel stronger, longer-lasting effects from the same cup. People with anxiety disorders, heart arrhythmias, acid reflux, or insomnia often do better at half the adult guideline or less. The 200mg figure this calculator uses for sensitive adults is a conservative starting point, not an official guideline; your own comfortable level may be lower. If caffeine worsens your anxiety, see our guide to caffeine and anxiety.

This tool is not medical advice. It summarizes published guidelines from the FDA, EFSA, AAP, ACOG, and CDC, which are population-level figures rather than personal prescriptions. People with heart conditions, anxiety disorders, high blood pressure, or who take medications that interact with caffeine should ask their doctor what is right for them.

Frequently Asked Questions

No. The FDA's 400mg figure applies to healthy, non-pregnant adults. Pregnant women are advised to stay under 200mg (ACOG), breastfeeding mothers under about 300mg (CDC), and adolescents under 100mg (AAP). Lighter adults also hit the equivalent dose sooner: EFSA's weight-based guidance of 5.7mg/kg per day works out to about 340mg for a 60kg person. And slow caffeine metabolizers, people with anxiety, heart rhythm issues, or sleep problems often feel adverse effects well below any of these numbers.

This calculator uses EFSA's per-kilogram figures: up to 5.7mg of caffeine per kilogram of body weight per day, and up to 3mg/kg in a single sitting, raise no safety concern for healthy adults. Multiply your weight in kilograms by 5.7 for your daily figure (a 70kg adult gets 399mg, which is where the familiar 400mg comes from) and by 3 for your single-dose figure (210mg for the same adult). For adolescents the calculator uses 3mg/kg per day, capped at the AAP's 100mg recommendation.

Common signs include jitteriness, a racing or pounding heart, anxiety, upset stomach, headache, and trouble falling asleep that night. The FDA notes that rapid consumption of around 1,200mg can cause toxic effects like seizures, but problems with sleep and anxiety start far lower for most people. If you regularly notice these symptoms, treat them as your real personal limit regardless of what the guideline says, and try our guide on how to cut back on caffeine without withdrawal.

Yes. Caffeine's half-life averages about 5 hours in healthy adults, so half of an afternoon coffee is still circulating at bedtime even if your daily total was within limits. Staying under your daily limit protects you from acute effects; stopping caffeine 8 or more hours before bed protects your sleep. Use the caffeine half-life calculator to see when your last drink clears, or the coffee cutoff time calculator to work backward from your bedtime.

Milligram for milligram, the caffeine is the same, but energy drinks make limits easier to blow through: a single can ranges from 80mg (Red Bull) to 300mg (Bang), they are often consumed quickly and cold rather than sipped hot, and sugar or other stimulant ingredients can mask how much you have had. That is why the AAP says children and teens should avoid energy drinks entirely, and why a single high-caffeine can plus a morning coffee can put even a healthy adult over 400mg.

Caffeine Safe Limit Calculator

🧑 Step 1: Who is this limit for?

☕ Step 2: Tally today's drinks against it