CaffeineTime

Caffeine in drinks

How much caffeine is in Oolong tea?

Data checked against the source on 2026-10-03 by Oleksii Y.

One 1 cup (240 g) of Oolong tea has 38.4 mg of caffeine, according to USDA Agricultural Research Service, FoodData Central (FNDDS).

How Oolong tea compares

  • Strength: 16 mg per 100 g.
  • One 1 cup (240 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, 6 have more caffeine per serving and 11 have less.

How much will be left at bedtime?

1 × 1 cup (240 g) of Oolong tea

Left at 11:00 PM (8 h later), average metabolism

≈ 13 mg

Range 6–19 mg (fast to slow metabolism)

38 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 Oolong 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 (240 g) of Oolong tea (38 mg), about 19 mg is still in your body 5 hours later and about 10 mg after 10 hours. If you clear caffeine slowly (an 8-hour half-life), about 16 mg is left after 10 hours.

Estimated caffeine left at 11:00 PM from one 1 cup (240 g) (38 mg), using a half-life of 5 hours for average metabolism and 3 to 8 hours for the range. How we calculate

Had atLeft at bedtime (average)Range
8:00 AM (15 h before bed)≈ 5 mg1–10 mg
12:00 PM (11 h before bed)≈ 8 mg3–15 mg
3:00 PM (8 h before bed)≈ 13 mg6–19 mg
6:00 PM (5 h before bed)≈ 19 mg12–25 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 10 servings.
  • Up to 200 mg at one time for healthy adults (EFSA): about 5 servings in one go.
  • Up to 200 mg a day in pregnancy (EFSA, NHS): about 5 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

CSPI's chart lists most brands of oolong tea at 30 to 40 mg per 6 oz.

How the serving amount was worked out: USDA lists 16 mg per 100 g; 240 g × 0.16 = 38.4 mg (FDC 2710492). The SR Legacy record (FDC 174120, 2 samples, min 14, max 19) gives 33.6 to 45.6 mg per 240 g cup.

Oolong tea vs other tea drinks

  • Black tea: Oolong tea has less caffeine than black tea per 100 g (16 vs 20 mg). Oolong tea: 38.4 mg per 1 cup (240 g); Black tea: 47.4 mg per 8 fl oz cup (237 g).
  • Green tea: Oolong tea has more caffeine than green tea per 100 g (16 vs 12 mg). Oolong tea: 38.4 mg per 1 cup (240 g); Green tea: 29.4 mg per 1 cup (245 g).
  • White tea: Oolong tea has more caffeine than white tea per typical serving. Oolong tea: 38.4 mg per 1 cup (240 g); White tea: 15–20 mg per 6 fl oz cup.

Common questions

How much caffeine is in Oolong tea?

USDA Agricultural Research Service, FoodData Central (FNDDS) gives 38.4 mg of caffeine per 1 cup (240 g).

How many Oolong 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 38.4 mg per 1 cup (240 g), that is about 10 servings if Oolong tea is your only source. In pregnancy the reference is 200 mg a day.

How late can I drink Oolong tea?

One serving has about 38 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 Oolong tea have more caffeine than Black tea?

Oolong tea has less caffeine than black tea per 100 g (16 vs 20 mg). Oolong tea: 38.4 mg per 1 cup (240 g); Black tea: 47.4 mg per 8 fl oz cup (237 g).

How long does Oolong tea stay in your system?

Of the 38 mg in one 1 cup (240 g), roughly 19 mg remains after 5 hours and 10 mg after 10 hours with our average 5-hour half-life. From fast to slow metabolism, 10 hours later it is between 4 and 16 mg.

Where the number comes from

  • Tea, hot, leaf, oolong. USDA Agricultural Research Service, FoodData Central (FNDDS). FDC ID 2710492, nutrient "Caffeine" (262): portion "1 cup" = 240 g. Accessed 2026-10-02. Source ↗
  • Beverages, tea, Oolong, brewed. USDA Agricultural Research Service, FoodData Central (SR Legacy). FDC ID 174120, nutrient "Caffeine" (262): 16 mg per 100 g, 2 samples, min 14, max 19. Accessed 2026-10-02. Source ↗
  • Caffeine chart. Center for Science in the Public Interest. row "Oolong tea, most brands | 6 oz. | 30–40" 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

  1. U.S. Food and Drug Administration (2024). Spilling the Beans: How Much Caffeine is Too Much? FDA Consumer Updates. fda.gov ↗
  2. European Food Safety Authority. Caffeine | EFSA. EFSA topic page (summary of the 2015 Scientific Opinion on the safety of caffeine). efsa.europa.eu ↗
  3. NHS. Foods to avoid in pregnancy. NHS. nhs.uk ↗

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