Caffeine in drinks
How much caffeine is in Green tea?
Data checked against the source on 2026-10-03 by Oleksii Y.
One 1 cup (245 g) of Green tea has 29.4 mg of caffeine, according to USDA Agricultural Research Service, FoodData Central (SR Legacy).
How Green tea compares
- Strength: 12 mg per 100 g.
- One 1 cup (245 g) has as much caffeine as about a quarter to a third of a cup of brewed coffee, which has 94.8 mg per 8 fl oz cup.
- Of the 17 other teas in our tea chart, 9 have more caffeine per serving and 8 have less.
How much will be left at bedtime?
1 × 1 cup (245 g) of Green tea
Left at 11:00 PM (8 h later), average metabolism
≈ 10 mg
Range 5–15 mg (fast to slow metabolism)
29 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
How long does Green 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 1 cup (245 g) of Green tea (29 mg), about 15 mg is still in your body 5 hours later and about 7 mg after 10 hours. If you clear caffeine slowly (an 8-hour half-life), about 12 mg is left after 10 hours.
Estimated caffeine left at 11:00 PM from one 1 cup (245 g) (29 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) | ≈ 4 mg | 1–8 mg |
| 12:00 PM (11 h before bed) | ≈ 6 mg | 2–11 mg |
| 3:00 PM (8 h before bed) | ≈ 10 mg | 5–15 mg |
| 6:00 PM (5 h before bed) | ≈ 15 mg | 9–19 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 13 servings.
- Up to 200 mg at one time for healthy adults (EFSA): about 6 servings in one go.
- Up to 200 mg a day in pregnancy (EFSA, NHS): about 6 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
The FDA lists 37 mg of caffeine for a 12 fl oz serving of green tea.
How the serving amount was worked out: USDA lists 12 mg per 100 g (6 analysed samples, min 8, max 18); 245 g × 0.12 = 29.4 mg. The sample min and max give 19.6 to 44.1 mg per cup.
Green tea vs other tea drinks
- Black tea: Green tea has less caffeine than black tea per 100 g (12 vs 20 mg). Green tea: 29.4 mg per 1 cup (245 g); Black tea: 47.4 mg per 8 fl oz cup (237 g).
- Oolong tea: Green tea has less caffeine than oolong tea per 100 g (12 vs 16 mg). Green tea: 29.4 mg per 1 cup (245 g); Oolong tea: 38.4 mg per 1 cup (240 g).
- White tea: Green tea has more caffeine than white tea per typical serving. Green tea: 29.4 mg per 1 cup (245 g); White tea: 15–20 mg per 6 fl oz cup.
Common questions
How much caffeine is in Green tea?
USDA Agricultural Research Service, FoodData Central (SR Legacy) gives 29.4 mg of caffeine per 1 cup (245 g).
How many Green 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 29.4 mg per 1 cup (245 g), that is about 13 servings if Green tea is your only source. In pregnancy the reference is 200 mg a day.
How late can I drink Green tea?
One serving has about 29 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.
Does Green tea have more caffeine than Black tea?
Green tea has less caffeine than black tea per 100 g (12 vs 20 mg). Green tea: 29.4 mg per 1 cup (245 g); Black tea: 47.4 mg per 8 fl oz cup (237 g).
How long does Green tea stay in your system?
Of the 29 mg in one 1 cup (245 g), roughly 15 mg remains after 5 hours and 7 mg after 10 hours with our average 5-hour half-life. From fast to slow metabolism, 10 hours later it is between 3 and 12 mg.
Where the number comes from
- Beverages, tea, green, brewed, regular. USDA Agricultural Research Service, FoodData Central (SR Legacy). FDC ID 171917, nutrient "Caffeine" (262): portion "1 cup" = 245 g. Accessed 2026-10-02. Source ↗
- Spilling the Beans: How Much Caffeine Is Too Much? U.S. Food and Drug Administration. Table "Typical Caffeine Content in 12-fluid-ounce Drinks", row "green tea" 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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