Three cups of chai, one filter coffee, a cola after lunch and a few squares of dark chocolate: is that too much caffeine for one day? You do not need a lab to find out. You only need a few numbers per drink and some simple addition.
The daily limit you are measuring against
The European Food Safety Authority says that up to 400 mg of caffeine a day does not raise safety concerns for healthy adults who are not pregnant. Health Canada gives the same 400 mg ceiling for adults.
The limit is lower for some groups:
- Pregnant or breastfeeding women: up to 200 mg a day, according to the EFSA and the American College of Obstetricians and Gynecologists (Health Canada sets 300 mg).
- Children aged 12 and under: Health Canada recommends no more than 2.5 mg per kilogram of body weight per day.
How much caffeine is in each drink
Caffeine content varies a lot, so use ranges and a sensible middle value:
- Tea: 30 to 90 mg per 250 ml cup. Black tea leaves hold 22 to 28 mg of caffeine per gram, green tea 11 to 20 mg per gram.
- Filter coffee: a median of 112 mg per 225 ml cup.
- Instant coffee: a median of 66 mg for the same cup size (anywhere from 29 to 117 mg).
- Espresso: 80 to 100 mg for a single 30 ml shot of arabica.
- Cola and other soft drinks: 0 to 55 mg per 350 ml serving.
- Energy drinks: from 80 mg per serving.
- Dark chocolate (70 to 85% cocoa): 80 mg per 100 g. Milk chocolate has 20 mg per 100 g.
- Decaf coffee: about 10 mg per cup, not zero.
The method: cups times caffeine, then add it up
For each drink, multiply the number of servings by the caffeine per serving. Then add every line together and compare the total with your limit.
Daily caffeine = (servings of drink 1 × mg per serving) + (servings of drink 2 × mg per serving) + …
For chai made with loose black tea, you can work it out from the leaves: grams of tea leaves × about 25 mg (the middle of the 22 to 28 mg range).
A real example, step by step
Take the day from the start, with chai made from say 2 g of black tea leaves per cup:
- 3 cups of chai: 3 × 2 g × 25 mg = 150 mg (between 132 and 168 mg depending on the leaves)
- 1 filter coffee: 112 mg
- 1 cola (350 ml), counted at the top of the range: 55 mg
- 50 g of 70% dark chocolate: half of 80 mg = 40 mg
Total: 150 + 112 + 55 + 40 = 357 mg. That is about 89% of the 400 mg adult limit, so this day stays inside it, with only 43 mg to spare. One energy drink on top would push it over.
For someone who is pregnant, the same day is 157 mg above the 200 mg limit, almost 1.8 times the recommended maximum. Swapping the filter coffee for an instant one saves about 46 mg, and dropping the cola saves up to 55 mg more.
For a child weighing 30 kg, the limit is 30 × 2.5 = 75 mg. A cola and 50 g of dark chocolate already add up to 95 mg.
When you drink it matters too
In healthy adults, caffeine has a half-life of 3 to 7 hours: that is the time your body needs to clear half of it. With a middle value of 5 hours, a 112 mg filter coffee at 4 pm still leaves about 56 mg in your body at 9 pm, and about 28 mg at 2 am. Caffeine can disturb sleep at doses as low as 100 mg a day, so the afternoon cup counts more than you might think. The half-life roughly doubles for women on the contraceptive pill and can reach 15 hours late in pregnancy.
Common mistakes when counting caffeine
- Counting cups, not cup size. Home coffee cups range from about 170 to 285 ml, so a big mug can hold far more than a small cup.
- Judging tea by its colour. Colour is a very poor indicator of caffeine: some pale green teas contain far more than dark smoky ones.
- Forgetting hidden sources. Cola, chocolate, energy drinks and some painkillers (which can include 100 to 130 mg of caffeine) all count.
- Treating decaf as caffeine free. Around 10 mg per cup is small, but it adds up over several cups.
If you are also watching what goes into your chai, the same add-it-up approach works for sugar: see how much sugar a day is too much, in teaspoons.
