How many cups of coffee a day is too many? The US Food and Drug Administration cites 400 milligrams a day for healthy adults, an amount it says is not generally associated with negative effects. In coffee that is about two to three 12-fluid-ounce (about 355ml) cups. But one cup can hold more than twice as much as another, and children, pregnancy and pure caffeine products carry their own warnings. This sets out the FDA page “Spilling the Beans: How Much Caffeine is Too Much?”.
1. 400mg a day for healthy adults. About two to three 12-ounce cups of coffee, the FDA says, an amount not generally linked to negative effects.
2. A cup of coffee holds 113 to 247mg. More than a twofold spread at the same 12 ounces. Decaf still has 2 to 15mg in an 8-ounce cup.
3. Pure caffeine is dangerous at less than half a teaspoon. Toxic effects such as seizures can follow rapid consumption of around 1,200mg.
Caffeine by drink — the FDA table
| Drink (12 oz, about 355ml) | Caffeine (FDA) | To reach 400mg (our arithmetic) |
|---|---|---|
| Caffeinated soft drink | 23 to 83mg | About 4.8 at the high end |
| Green tea | 37mg | About 10.8 |
| Black tea | 71mg | About 5.6 |
| Coffee (regular brewed) | 113 to 247mg | About 1.6 at the high end, about 3.5 at the low end |
| Energy drink | 41 to 246mg | About 1.6 at the high end |
The middle column is the FDA table; the right column is 400 divided by it, our arithmetic. Converting 12 ounces to 355ml is ours too (1 ounce is about 29.6ml). The FDA separately gives 54 to 328mg per 16 ounces (about 473ml) for energy drinks. The caffeine in a cup from a Korean coffee shop is not on this page and is not given here — it depends on cup size and shots.
Decaf is not zero
The FDA says decaffeinated coffee and tea have less caffeine than regular versions but still contain some, typically 2 to 15mg in an 8-ounce (about 237ml) cup of decaf coffee. Anyone who must avoid caffeine should not read “decaf” as zero (our reading).
Too much — the symptoms the FDA lists
- Increased heart rate or palpitations
- High blood pressure
- Insomnia or sleep disruption
- Anxiety, jitters
- Upset stomach, nausea, headache
For the sleep side, see how much sleep you need.
People and products with their own warnings
Children and teens
The FDA says medical experts advise against energy drinks for children and teens because of their sugar and caffeine. Too much caffeine in children and teens can cause a raised heart rate, palpitations, high blood pressure and anxiety, and the US Dietary Guidelines say drinks containing caffeine should be avoided for children younger than 2.
Pregnancy and breastfeeding
If you are pregnant, trying to become pregnant or breastfeeding, the page recommends talking to your health care provider. It gives no separate figure.
Pure and highly concentrated caffeine
Toxic effects such as seizures can be seen with rapid consumption of around 1,200mg, which the FDA says is less than half a teaspoon of pure caffeine, and these products can have serious consequences including death. 1,200mg is three times the 400mg figure (our arithmetic).
Checklist
- ☐ Coffee, tea, soft drinks and energy drinks together near 400mg a day?
- ☐ Coffee ranges widely, 113 to 247mg a cup
- ☐ No energy drinks for children; no caffeinated drinks under 2
- ☐ Pregnant or breastfeeding: ask your clinician
- ☐ Avoid pure caffeine powders and liquids
Questions that remain
Does Korea use a different limit?
Only the FDA page was read for this article. Age-based recommendations from Korean agencies were not checked in the original and are not given.
Can coffee count instead of water?
How much to drink a day and how drinks are counted is in how much water a day.
The NHS says to avoid caffeinated drinks with chilblains, as caffeine affects blood flow to the hands and feet (chilblains).
The NHS lists coffee among drinks that can trigger heartburn (heartburn and acid reflux).
For insomnia, the NHS says not to drink tea or coffee for at least 6 hours before bed (insomnia).
Sources
- U.S. FDA — Spilling the Beans: How Much Caffeine is Too Much? — original (page shows: Content current as of 08/28/2024; checked 12 October 2026). 400mg, two to three 12-ounce cups, caffeine by drink, decaf 2 to 15mg, symptoms, children and pregnancy, 1,200mg and half a teaspoon.
- Not read. Korean agencies' caffeine recommendations in the original; caffeine in Korean coffee-shop drinks.
- Our arithmetic. Ounce-to-ml conversions, cups to 400mg, 1,200mg being three times 400mg.
Where to check further
- The product label — total caffeine.
- Your clinician if pregnant or breastfeeding.
Written 12 October 2026. The content sets out the FDA original; conversions and arithmetic are ours. It does not replace diagnosis or treatment.
