Enter your bedtime and drink to see the latest time to have it, and how much caffeine will still be in your body when you go to bed.
Your body breaks caffeine down steadily. The time it takes to remove half of it is called its half-life. In healthy adults it’s about 5 hours on average, but it ranges from about 2 to 10 hours. It is longer during pregnancy and with some medicines, including oral contraceptives, and shorter in people who smoke.
We recommend whichever is earlier: at least 6 hours before bed, or the time it takes for the caffeine from your drink to drop below 50 mg, about half a cup of coffee. For a strong drink, that can be 10 hours or more. The 6-hour rule comes from a 2013 study in the Journal of Clinical Sleep Medicine: 400 mg of caffeine taken 6 hours before bed still cut sleep by more than an hour, even though participants didn’t notice it.
| Drink | Typical caffeine |
|---|---|
| Brewed coffee, 8 oz (240 ml) | 80–100 mg |
| Espresso, single shot | about 64 mg |
| Black tea, 8 oz | about 47 mg |
| Green tea, 8 oz | about 28 mg |
| Energy drink, 8.4 oz (250 ml) | about 80 mg |
| Cola, 12 oz can | 30–40 mg |
| Decaf coffee, 8 oz | 2–15 mg |
| Dark chocolate, 1 oz | about 12 mg |
Amounts vary a lot by brand and how the drink is made. The US Food and Drug Administration says up to 400 mg a day is not generally linked to harmful effects for most healthy adults.
For general information only, not medical advice. If you often feel tired despite enough sleep, snore loudly, or have trouble sleeping most nights, talk to a doctor.