Caffeine in drinks
How much caffeine is in Black tea?
Data checked against the source on 2026-10-03 by Oleksii Y.
One 8 fl oz cup (237 g) of Black tea has 47.4 mg of caffeine, according to USDA Agricultural Research Service, FoodData Central (SR Legacy).
How Black tea compares
- Strength: 20 mg per 100 ml.
- One 8 fl oz cup (237 g) has as much caffeine as about half a cup of brewed coffee, which has 94.8 mg per 8 fl oz cup.
- Of the 17 other teas in our tea chart, 4 have more caffeine per serving and 13 have less.
How much will be left at bedtime?
1 × 8 fl oz cup (237 g) of Black tea
Left at 11:00 PM (8 h later), average metabolism
≈ 16 mg
Range 7–24 mg (fast to slow metabolism)
47 mg is already at or under the 50 mg this tool aims to have left at bedtime.
What sleep studies found near this dose
- Gardiner et al. 2025 (randomized trial): In 23 healthy young men, 100 mg taken 12, 8 or 4 hours before bed had no significant effect on measured or self-rated sleep.
- Gardiner et al. 2023 (meta-analysis): To avoid losing sleep time, the authors suggest a coffee (107 mg per 250 ml) at least 8.8 hours before bed.
Estimate from a simple model: half-life of 3, 5 or 8 hours, 50 mg bedtime target. How we calculate
Caffeine by size
| Serving | Caffeine |
|---|---|
| 8 fl oz cup (237 g) | 47.4 mg |
| 6 fl oz cup (178 g) | 35.6 mg |
How long does Black tea stay in your system?
Our model halves caffeine every 5 hours for average metabolism, and every 3 or 8 hours for fast or slow metabolism. From one 8 fl oz cup (237 g) of Black tea (47 mg), about 24 mg is still in your body 5 hours later and about 12 mg after 10 hours. If you clear caffeine slowly (an 8-hour half-life), about 20 mg is left after 10 hours.
Estimated caffeine left at 11:00 PM from one 8 fl oz cup (237 g) (47 mg), using a half-life of 5 hours for average metabolism and 3 to 8 hours for the range. How we calculate
| Had at | Left at bedtime (average) | Range |
|---|---|---|
| 8:00 AM (15 h before bed) | ≈ 6 mg | 1–13 mg |
| 12:00 PM (11 h before bed) | ≈ 10 mg | 4–18 mg |
| 3:00 PM (8 h before bed) | ≈ 16 mg | 7–24 mg |
| 6:00 PM (5 h before bed) | ≈ 24 mg | 15–30 mg |
How many fit in a day?
Reference amounts are for caffeine from all sources combined. Counted at the upper end of the stated amount, one serving at a time:
- Up to 400 mg a day for most healthy adults (FDA, EFSA): about 8 servings.
- Up to 200 mg at one time for healthy adults (EFSA): about 4 servings in one go.
- Up to 200 mg a day in pregnancy (EFSA, NHS): about 4 servings.
These are reference amounts for groups of people, not a personal limit. Some people feel jittery or sleep worse on much less. See the cutoff calculator for timing.
Good to know
A lab study of brewed teas found that steeping time changed how much caffeine ended up in the cup.
How the serving amount was worked out: USDA lists 20 mg per 100 g (41 analysed samples); 237 g × 0.20 = 47.4 mg; 178 g × 0.20 = 35.6 mg.
Black tea vs other tea drinks
- Green tea: Black tea has more caffeine than green tea per 100 g (20 vs 12 mg). Black tea: 47.4 mg per 8 fl oz cup (237 g); Green tea: 29.4 mg per 1 cup (245 g).
- Oolong tea: Black tea has more caffeine than oolong tea per 100 g (20 vs 16 mg). Black tea: 47.4 mg per 8 fl oz cup (237 g); Oolong tea: 38.4 mg per 1 cup (240 g).
- White tea: Black tea has more caffeine than white tea per 6 fl oz cup (178 g): 35.6 mg vs 15–20 mg.
Common questions
How much caffeine is in Black tea?
USDA Agricultural Research Service, FoodData Central (SR Legacy) gives 47.4 mg of caffeine per 8 fl oz cup (237 g). Other sizes are in the table on this page.
How many Black tea servings can I have in a day?
The FDA and EFSA cite up to 400 mg of caffeine a day, from all sources combined, for most healthy adults. At 47.4 mg per 8 fl oz cup (237 g), that is about 8 servings if Black tea is your only source. In pregnancy the reference is 200 mg a day.
How late can I drink Black tea?
One serving has about 47 mg, which is at or under the 50 mg our calculator aims to have left at bedtime, so it sets no cutoff for a single serving. Several servings add up.
How long does Black tea stay in your system?
Of the 47 mg in one 8 fl oz cup (237 g), roughly 24 mg remains after 5 hours and 12 mg after 10 hours with our average 5-hour half-life. From fast to slow metabolism, 10 hours later it is between 5 and 20 mg.
Where the number comes from
- Beverages, tea, black, brewed, prepared with tap water. USDA Agricultural Research Service, FoodData Central (SR Legacy). FDC ID 173227, nutrient "Caffeine" (262): portions "1 cup (8 fl oz)" = 237 g and "6 fl oz" = 178 g. Accessed 2026-10-02. Source ↗
- Caffeine content of brewed teas. Journal of Analytical Toxicology. PMID 19007524, abstract. Accessed 2026-10-02. Source ↗
Recipes and labels change. If a number here no longer matches the label, the label wins.
General information, not medical advice
If you feel unwell after caffeine — for example chest pain, a fast or irregular heartbeat that does not settle, fainting, confusion or trouble breathing — get urgent medical help. If you are pregnant, take medication or have a heart, liver or anxiety condition, ask a doctor or pharmacist what amount is right for you.
Sources
- U.S. Food and Drug Administration (2024). Spilling the Beans: How Much Caffeine is Too Much? FDA Consumer Updates. fda.gov ↗
- European Food Safety Authority. Caffeine | EFSA. EFSA topic page (summary of the 2015 Scientific Opinion on the safety of caffeine). efsa.europa.eu ↗
- NHS. Foods to avoid in pregnancy. NHS. nhs.uk ↗
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