Caffeine Intake Calculator
＋More features: caffeine left at bedtime, time for your last cup
How much is left when you go to bed?
From the time you drink, the number of cups and your planned bedtime, estimates the caffeine left at bedtime using a half-life of about 5 hours (1 cup = 150 ml ≒ 90 mg).
By when should you finish drinking?
From the cups and bedtime above, works backwards to the time for your last cup so that less than 100 mg (a level that tends to affect sleep) remains at bedtime.
Just enter what you drank and how much to see your total caffeine for the day. You can also check whether it is too much compared with the daily guide (400 mg for a healthy adult). A handy over-consumption check for people who drink a lot of coffee or energy drinks.
How to use
- Enter what you drank (coffee, tea, energy drink, etc.) and the amount (ml).
- Use “+ Add a drink” to enter a whole day’s drinks at once.
- As you type, the total in mg and the percentages of the daily guides appear right below. Changing a drink recalculates instantly.
How it is calculated
- Caffeine (mg) = concentration (mg/100 ml) × amount (ml) ÷ 100, summed over all drinks
- Concentrations use values such as those in the Standard Tables of Food Composition in Japan (brewed): coffee 60 / instant 57 / black tea 30 / sencha, hojicha and oolong tea 20 / gyokuro 160 / cola about 10 mg/100 ml
- Example: 2 cups of coffee (400 ml) + a 500 ml bottle of green tea = 240 + 100 = 340 mg (85% of the adult guide)
- Guide: up to 400 mg a day for healthy adults (assessments by the European Food Safety Authority and others). Less during pregnancy or breastfeeding (WHO says 300 mg; many agencies recommend 200 mg).
Sources and assumptions
- Caffeine concentrations in drinks and intake guides: Ministry of Agriculture, Forestry and Fisheries (Japan), “On excessive intake of caffeine” (includes assessments by Japan’s Food Safety Commission and overseas agencies), in Japanese
Assumptions and notes
- The caffeine in energy drinks varies greatly by product (30–300 mg per can). Check the product label for the exact amount.
- Sensitivity to caffeine varies greatly between people; some cannot sleep even after a small amount.
- If you regularly use caffeine tablets or anti-drowsiness drinks, or have any health concerns, consult a doctor or pharmacist.
Frequently asked questions
How many cups of coffee a day are OK?
One cup of drip coffee (150 ml) has about 90 mg, so the 400 mg guide for healthy adults corresponds to about 4–5 cups. Individual differences are large, though, and coffee later in the day affects sleep more easily — watch both the amount and the timing.
Until how many hours before bed can I drink coffee?
It takes about 4 hours (2–8 hours depending on the person) for the blood caffeine level to halve. If you feel it affects your sleep, it is safest to stop 5–6 hours before bedtime.
How much should I limit myself to during pregnancy?
The WHO recommends up to 300 mg a day, and many agencies such as those in the UK recommend up to 200 mg. This tool also shows the percentage of the 200 mg guide. If your doctor gives you instructions, follow those first.