How much caffeine is in your drinks
Caffeine content varies with the bean, the brewing method and the serving size. Typical amounts:
| Drink | Serving | Caffeine |
|---|---|---|
| Brewed coffee | 8 oz | 96 mg (80 to 200) |
| Espresso | 1 oz shot | 64 mg |
| Black tea | 8 oz | 47 mg |
| Green tea | 8 oz | 28 mg |
| Cola | 12 oz can | 34 mg |
| Energy drink | 8.4 oz can | 80 mg |
| Large coffeehouse brew | 16 oz | 250 to 330 mg |
Decaf coffee still contains 2 to 15 mg per cup, and dark chocolate about 12 mg per ounce. Add those under “Other caffeine” if you have a lot of them.
How much is safe
The FDA cites 400 mg a day for healthy adults as an amount not generally associated with dangerous effects. During pregnancy, the American College of Obstetricians and Gynecologists advises staying under 200 mg. The calculator also shows your intake per kilogram of body weight, since sensitivity rises in smaller people. Health agencies suggest children and teens keep below about 2.5 to 3 mg per kg, and many pediatricians advise teens to avoid energy drinks.
Worked example
You drink two cups of brewed coffee, one cup of black tea and one can of cola, weigh 160 lb and have your last drink 6 hours before bed.
- Total: 2 × 96 + 47 + 34 = 273 mg, or 68% of the 400 mg limit.
- Per kilogram: 273 ÷ 72.6 kg = 3.8 mg/kg.
- At bedtime, after a 5-hour half-life: 273 × 0.5^(6 ÷ 5) = 119 mg still in your body, about the same as one strong coffee.
Caffeine and sleep
Caffeine blocks adenosine, the chemical that builds sleep pressure during the day. Its half-life averages about 5 hours but ranges from 2 to 10 hours. It lasts longer in pregnancy, with liver disease and with some medications, and is shorter in smokers. A dose taken in the afternoon can still shorten deep sleep at night even if you fall asleep easily. Many sleep experts suggest stopping caffeine at least 8 hours before bed.
Signs of too much
Jitteriness, a racing heart, anxiety, an upset stomach, headaches and insomnia are common signs. Very high doses, such as caffeine powders or pills, can cause dangerous heart rhythms. One teaspoon of pure caffeine powder can contain as much as 28 cups of coffee.
Cutting back
Reduce gradually, by about half a cup a day, to avoid withdrawal headaches. Swap some cups for half-caf or decaf, and watch for hidden sources such as pre-workout supplements and some pain relievers.
This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.