How much is too much?
The U.S. FDA says up to about 400 mg a day is generally not linked to negative effects for most healthy adults. People who are pregnant, sensitive to caffeine, taking certain medicines or under 18 should aim lower; ask a doctor about your own limit.
How long it stays with you
Caffeine's half-life is about 5 hours on average (it ranges widely, from about 2 to 10 hours). Here is roughly how much is left after one serving:
| Hours later | Caffeine left |
|---|---|
| 0 h | 28 mg |
| 2 h | 21 mg |
| 4 h | 16 mg |
| 6 h | 12 mg |
| 8 h | 9 mg |
| 10 h | 7 mg |
| 12 h | 5 mg |
That is why an afternoon coffee can still affect sleep. The caffeine calculator adds up a whole day.
Compared with other drinks
| Drink | Serving | Typical caffeine |
|---|---|---|
| cold brew (16 oz) | 16 oz glass | 200 mg |
| nitro cold brew | 12 oz | 200 mg |
| brewed coffee (16 oz) | 16 oz cup | 190 mg |
| iced coffee (16 oz) | 16 oz glass with ice | 165 mg |
| brewed coffee (12 oz) | 12 oz cup | 140 mg |
| a mocha | 12 oz, 1–2 shots + chocolate | 130 mg |
| a double espresso | 2 oz double shot | 126 mg |
| a latte | 12 oz, 1–2 shots | 126 mg |
| a cappuccino | 8–12 oz, 1–2 shots | 126 mg |
| an americano | 12 oz, 2 shots | 126 mg |
| a flat white | 6–8 oz, 2 shots | 126 mg |
| a cortado | 4 oz, 2 shots | 126 mg |
| moka pot coffee | 2 oz serving | 105 mg |
| French press coffee | 8 oz cup | 100 mg |
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Take a lookQuestions people ask
How much caffeine is in green tea?
About 28 mg in a 8 oz cup serving, usually 20–45 mg.
How many servings of green tea can I have a day?
About 14 servings would reach 400 mg, the FDA's general guideline for healthy adults. Many people feel best well below that.
Numbers on this page are estimates calculated from the assumptions shown. Coffees, beans and drinks vary; caffeine figures are typical values, not medical advice.