Caffeine Calculator - Daily Intake and Half-Life
Daily caffeine total and an estimate of what is left in your body
Runs in your browser · nothing is uploaded
Updated 2026-10-04The two drinks already in the list (Americano 150 mg, energy drink 80 mg) are examples. Real products differ, so replace them with what you drank and the caffeine content on the label.
Who is it for
The daily maximum recommended by Korea's Ministry of Food and Drug Safety (MFDS), as reported in its press release, is 400 mg for adults, 300 mg for pregnant women and 2.5 mg per kg of body weight for children and teens.
What you drank
Enter the caffeine content printed on the label or listed by the seller (above 0 and up to 1,000 mg). The count can be a decimal such as 0.5 (above 0, up to 50). List drinks in the order you had them. A time earlier than the row above counts as the next day (a coffee at 23:00 followed by 01:00 means 1 a.m. the next day).
Drink 1(Example value)
Drink 2(Example value)
About 5 hours is the commonly cited average for healthy adults. It varies a lot with the person, pregnancy and medication. Enter 2 to 12 hours.
The calculator finds when caffeine in your body falls below this amount. The default 25 mg is just an example. Enter above 0 and up to 500 mg.
Total caffeine 230 mg, 57.5% of the daily maximum
Estimate
- Total caffeine
- 230mg
- Daily maximum recommended
- 400mg
- Share of the maximum
- 57.5%
- Room left
- 170mg
- Peak in your body (estimate)
- 150mg
- Right after the last drink (estimate)
- 145.3mg
- Time it drops below 25 mg (estimate)
- 03:42 (next day)
Your total is within the daily maximum. It is a daily-total guide and says nothing about how sensitive you personally are.
Estimated caffeine in your body (24 hours from the first drink)
| Time | After first drink | Caffeine (mg) |
|---|---|---|
| 09:00 | 0 h | 150 |
| 12:00 | 3 h | 99 |
| 15:00 | 6 h | 145.3 |
| 18:00 | 9 h | 95.9 |
| 21:00 | 12 h | 63.2 |
| 00:00 (next day) | 15 h | 41.7 |
| 03:00 (next day) | 18 h | 27.5 |
| 06:00 (next day) | 21 h | 18.2 |
| 09:00 (next day) | 24 h | 12 |
The math with your numbers
- Total = 150mg × 1 + 80mg × 1 = 230 mg
- Maximum = 400 mg (Adult)
- 230 mg / 400 mg x 100 = 57.5%
- In body(t) = sum of dose x 0.5^((t - dose time) / 5 h)
- 145.29 mg x 0.5^(x / 5 h) = 25 mg, so x = 5 x log2(145.29 / 25) = 12.69 h
This is a rough estimate for reference. It does not diagnose or treat anything. If you are worried about your health or sensitive to caffeine, talk to a doctor. The daily maximum comes from the MFDS press release. This tool has no table of caffeine per drink, so you need to take the amount from the product label. The amount left in your body assumes caffeine falls by a fixed fraction per half-life, a simple model that can be far off depending on the person, pregnancy, medication and liver function. Numbers are computed with decimals and rounded once, for display.
Source: the maximum daily intake recommendation in a press release by Korea's Ministry of Food and Drug Safety (https://www.korea.kr/briefing/pressReleaseView.do?newsId=156061464). The values were confirmed through a summary of the release and the full original was not checked. The roughly 5-hour half-life is general knowledge for healthy adults and is not tied to a specific paper. Retrieved 2026-10-04.
What it is
This calculator adds up the caffeine in everything you drank in a day and compares the total with the daily maximum from Korea’s Ministry of Food and Drug Safety. Drink names are free text, so Korean, Chinese and emoji all work. For each drink you enter the caffeine per serving in mg, how many servings and the time. You get your total, the share of the maximum and the room left. A simple half-life model then estimates how much caffeine is still in your body, drawn as a 24-hour graph with a table, and it finds the time it falls below a level you choose. The form opens with two example drinks so a result shows up straight away.
How to use
- Choose adult, pregnant or child and teen. For a child or teen, enter body weight in kg.
- For every drink, enter the caffeine per serving from the label, the number of servings and the time. Press Add a drink for more, up to 12. A new row stays out of the math until you enter its caffeine. List drinks in the order you had them: a time earlier than the row above counts as the next day, so a coffee at 23:00 followed by an energy drink at 01:00 is two hours later, and that row says so.
- Change the half-life and the level to wait for if you want.
- Read the total, the share of the maximum, the room left and the graph.
How it works
- The daily maximum is 400 mg for adults, 300 mg for pregnant women and 2.5 mg per kg for children and teens, as reported in an MFDS press release. A total counts as over the limit only when it is above the maximum, compared at the one decimal place shown on screen.
- The total is caffeine per serving times servings, summed over all rows. Servings can be decimals such as 0.5. Caffeine must be above 0 and at most 1,000 mg, and servings above 0 and at most 50.
- Caffeine in your body at time t is the sum over drinks of dose x 0.5^(t / half-life), counting only drinks already taken. Absorption is treated as instant, which is a simplification. The default half-life is 5 hours.
- The time to reach your chosen level is the half-life times log2 of (amount right after the last drink / level), added to the time of the last drink.
- There is no caffeine table for drinks. Every amount comes from you.
- Numbers are computed with decimals and rounded once, for display. Source retrieved 2026-10-04.
Examples
An adult has an Americano (150 mg) at 09:00 and an energy drink (80 mg) at 15:00. Both amounts are examples and real products differ.
| Item | Math | Result |
|---|---|---|
| Daily total | 150 + 80 | 230 mg |
| Share of the maximum | 230 / 400 x 100 | 57.5% |
| Room left | 400 - 230 | 170 mg |
| In the body right after 15:00 | 150 x 0.5^(6/5) + 80 | about 145.3 mg |
| Below 25 mg | 5 h x log2(145.3 / 25) | about 12.7 h later, 03:42 next day |
Good to know
This is a rough estimate for reference. It does not diagnose or treat anything. If you are sensitive to caffeine, pregnant, or have heart or sleep problems, talk to a doctor. The maximum is a daily-total guide and says nothing about your personal sensitivity, and the amount left in your body differs a lot between people. Energy drinks, medicines, chocolate and tea can contain caffeine too, so check the label.
FAQ
What is the daily caffeine maximum used here?
The figures reported in a press release from Korea's Ministry of Food and Drug Safety (MFDS) are 400 mg a day for adults, 300 mg for pregnant women and 2.5 mg per kg of body weight for children and teens. The values were confirmed through a summary of the release, not the full original.
Where does the caffeine per drink come from?
From you. The same kind of drink varies by brand and shop, so this tool has no built-in table. Copy the caffeine content from the product label or the seller's nutrition information. The 150 mg and 80 mg already in the form are examples only.
How is the caffeine left in my body estimated?
It assumes the amount halves every half-life. The default is about 5 hours, the commonly cited average for healthy adults, and you can change it from 2 to 12 hours. Real half-lives differ with the person, pregnancy and medication, and the default is general knowledge rather than a figure from one paper.
What does the time it drops below 25 mg mean?
It is the clock time when the estimated amount after your last drink falls under the level you chose. 25 mg is only an example and you can change it. If it falls after midnight the result is marked as the next day.
Can children or pregnant women use it?
Pick the group and the limit changes. It is still only a rough estimate and does not replace medical advice, so ask a doctor if you are pregnant or worried about a child's caffeine.
Is my input sent anywhere?
No. Everything is calculated in your browser.
