Caffeine Calculator

Your details

Used to calculate your personalised caffeine limit (mg per kg).
kg
Health guidelines cap daily caffeine differently by group: 400 mg for adults, 200 mg when pregnant, 100 mg for teenagers.
EFSA rates a single dose of 3 mg/kg as safe for all healthy adults. The FDA 400 mg cap corresponds to roughly 5.7 mg/kg for a 70 kg person.
Caffeine is metabolised by the CYP1A2 enzyme. Genetic variation, pregnancy and smoking all shift the half-life significantly.
servings
servings
servings
Used to estimate how much caffeine is still active in your body right now.
h
Caffeine at bedtime disrupts sleep onset and reduces deep sleep. Even 100 mg can shorten slow-wave sleep.
h
Total caffeine todayWithin limit
253mg

Sum of all servings you entered

Your daily limit399mg
Remaining allowance146mg
Over limit by0mg
Active in body now192mg
Caffeine at bedtime83mg
Percentage of limit used0.6%
0.6% % of limit
Low<0.5Within limit0.5-1Slightly over1-1.25Over limit1.25+
Active now192
At bedtime83
Remaining allowance146

You have had 253 mg of caffeine today, 146 mg below your estimated limit of 399 mg.

  • About 192 mg of caffeine is still active in your system right now based on your metabolism speed.
  • About 83 mg will remain at bedtime, a low level that may have a minor effect on sleep for sensitive individuals.

Next stepStay hydrated alongside caffeine: each cup of coffee increases mild dehydration slightly, especially during exercise.

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