How to use it
- Write each drink on its own line with the number of servings, for example espresso 2.
- Add a volume such as 330 ml for a can or bottle that is not the usual serving.
- Enter your bodyweight and read Total caffeine and Caffeine per kg of bodyweight.
- Check the status lines against the EFSA limits, and use the table of hours to see what is left later.
How the caffeine is calculated
Each drink uses the EFSA guideline amount for its serving: espresso 60 ml 80 mg, filter coffee 200 ml 90 mg, black tea 220 ml 50 mg, cola 355 ml 40 mg and energy drink 250 ml 80 mg. A different volume is scaled in proportion, which is an estimate and not a measurement. The caffeine left after t hours is the dose times one half raised to the power t divided by the half-life.
Caffeine of a drink = serving mg × (volume ÷ serving volume) × servings
Total (mg) = sum of all drinks
mg per kg = total ÷ bodyweight (kg)
Left after t hours = total × 0.5^(t ÷ half-life)- EFSA (2015) sets 400 mg a day for healthy adults, 3 mg per kg of bodyweight for a single dose, and 200 mg a day during pregnancy and breastfeeding.
- Turkish coffee is not in the EFSA guideline table, so it is not counted. Its caffeine depends strongly on how it is made, and this tool does not guess a value for it.
What this calculator does not include
Half-life varies from person to person. Published figures for healthy adults run from about 3 to 7 hours, and pregnancy, some medicines and the contraceptive pill lengthen it. The 5-hour default is a midpoint, so use your own range if you know it.
Chocolate, tea blends, painkillers and energy shots are not all in the table. Read the label on a product that is not listed. This is general information and not medical advice; ask a doctor if caffeine affects your heart, sleep or pregnancy.
Worked example: 2 espressos and a 330 ml cola, 70 kg
Two espressos give 2 × 80 = 160 mg. A 330 ml cola is 40 × 330 / 355 = 37.2 mg, so the total is 197.2 mg. That is 197.2 / 70 = 2.82 mg per kg, well within the 400 mg daily limit and the 210 mg single-dose figure for 70 kg.
With a 5-hour half-life, 197.2 mg falls to 98.6 mg after 5 hours and to 7.1 mg after 24 hours.
| Hours after | Caffeine left (mg) |
|---|---|
| 0 | 197.2 |
| 2 | 149.4 |
| 4 | 113.3 |
| 6 | 85.8 |
| 8 | 65.1 |
| 10 | 49.3 |
| 12 | 37.4 |
| 24 | 7.1 |
Frequently asked questions
How much caffeine is safe in a day?
EFSA's 2015 scientific opinion says intakes up to 400 mg a day do not raise safety concerns for healthy adults. Pregnant and breastfeeding women are given 200 mg a day.
Why is there a single-dose limit as well?
EFSA gives a single dose of about 3 mg per kg of bodyweight, so a lighter person should take less at one time even when the daily total is within the limit. The calculator checks the largest single serving.
Why is Turkish coffee not in the table?
The EFSA guideline table lists espresso, filter coffee, black tea, cola and energy drink. Turkish coffee differs a lot between cups, and this tool does not guess its caffeine, so it is left out and reported.
What does the half-life mean for me?
It is the time for half of the caffeine to leave your body. A drink at 4 pm can still leave about half its caffeine by 9 pm if the half-life is 5 hours, which can affect sleep.
Does this tool keep what I type?
No. The calculation runs in your browser and nothing you enter is stored or sent to us.
Sources
- EFSA: Caffeine, topic page with the 2015 scientific opinion summary (limits, single dose, guideline amounts per serving)
- Wikipedia: Caffeine (half-life in healthy adults, 3 to 7 hours, and in pregnancy)
Figures and text last checked on Tuesday, November 10, 2026.