Caffeine Intake Calculator

Estimate daily caffeine intake from coffee, tea, energy drinks, and body-weight-based guidance.

Daily caffeine

235 mg

Within guidance

Guidance

400 mg

Weight-based cap, not medical advice

Remaining

165 mg

Negative means above guidance

Coffee equivalent

2.5 cups

95 mg per cup

Caffeine inputs

Estimate caffeine intake from coffee, tea, and energy drinks.

Body weight

Coffee cups

Caffeine per coffee

Tea cups

Caffeine per tea

Energy drinks

Caffeine per energy drink

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What is the caffeine intake calculator?

This calculator totals daily caffeine from coffee, tea, energy drinks, soda, chocolate, and other products. It compares intake with a personalized daily limit and estimates how late caffeine can be consumed without affecting sleep.

The Korean source uses a caffeine database for common beverages and accounts for user group, body weight, sensitivity, pregnancy, and bedtime.

Recommended daily limits

2026 reference limits

Healthy adults: 400 mg per day, referenced to FDA and EFSA style guidance.
Pregnant and lactating users: 200 mg per day because of fetal or infant exposure concerns.
Teenagers from 13 to 18: body weight kg x 2.5 mg. A 50 kg teenager is about 125 mg per day.
Children from 4 to 12 also use body weight kg x 2.5 mg, but the guide recommends minimizing intake where possible.
Caffeine is absorbed within about 15 to 45 minutes, so effects can appear quickly after drinking.

Common caffeine amounts

Espresso 30 mL: about 63 mg.
Americano 355 mL: about 150 mg.
Brewed coffee 240 mL: about 95 mg; cold brew 355 mL: about 200 mg.
Green tea 240 mL: about 28 mg; black tea 240 mL: about 47 mg; matcha 240 mL: about 70 mg.
Red Bull 250 mL: about 80 mg; Monster 355 mL: about 160 mg; Bacchus D 120 mL: about 30 mg.
Decaffeinated coffee is not zero caffeine; a cup can still contain roughly 2 to 15 mg.

Half-life and sleep impact

Caffeine elimination

Caffeine half-life is the time for blood caffeine concentration to fall by half.
The average adult half-life is about 5 hours, but the guide uses a possible range of 3 to 7 hours.
Pregnancy can extend half-life to about 9 to 11 hours.
Smoking can shorten half-life to about 3 to 4 hours, while oral contraceptives can roughly double it.
C(t) = C0 x (0.5)^(t / half-life). After 200 mg and a 5-hour half-life, about 100 mg remains after 5 hours and 50 mg after 10 hours.

Last safe intake time

The sleep-impact threshold is modeled as 25 mg or less at bedtime.
If an Americano contains 150 mg, half-life is 5 hours, and bedtime is 23:00, the calculator needs about 12.9 hours to drop below 25 mg.
That example makes the last safer caffeine time about 10:00.
The guide recommends avoiding caffeine after roughly 14:00 for ordinary sleep hygiene and reducing intake gradually by about 25% per week to avoid withdrawal symptoms.