How much caffeine is in Green tea?

One 240 ml cup of green tea contains 28 mg of caffeine.

Caffeine is a naturally occurring stimulant found in tea leaves and coffee beans; this definition of caffeine is authoritative and used across public health sources (TrackCaffeine dataset).

The concentration works out to 11.7 mg per 100 ml for this 240 ml serving, where the 11.7 mg per 100 ml figure is calculated from the TrackCaffeine dataset value of 28 mg per 240 ml (TrackCaffeine dataset).

Compared with a standard 240 ml cup of drip coffee at 96 mg, this green tea provides 0.3× the caffeine of drip coffee, where the drip coffee 96 mg reference is taken from the TrackCaffeine dataset (TrackCaffeine dataset).

A single 28 mg cup is a low-to-moderate stimulant dose: most healthy adults report mild alerting effects from tens of milligrams of caffeine according to clinical summaries (Mayo Clinic caffeine chart), and public guidance frames 400 mg per day as an upper limit for healthy adults (U.S. FDA).

How long Green tea stays in your system

TrackCaffeine models caffeine elimination as first-order elimination, meaning the fraction of caffeine removed per unit time is constant; this definition of first-order elimination is used in our decay calculations (TrackCaffeine model, population-average half-life 5.7 hours).

The decay formula used is remaining = dose × 0.5^(hours / 5.7), where the 5.7-hour half-life is the TrackCaffeine population-average parameter (TrackCaffeine model, 5.7 hours). For a 28 mg dose this becomes remaining = 28 × 0.5^(hours / 5.7) (TrackCaffeine model).

Applying the formula to this 28 mg dose yields: after 3 hours remaining = 28 × 0.5^(3/5.7) ≈ 18.6 mg (rounded to 19 mg) as calculated with the TrackCaffeine half-life; after 6 hours remaining = 28 × 0.5^(6/5.7) ≈ 13.3 mg (rounded to 13 mg) per the TrackCaffeine model; after 9 hours remaining = 28 × 0.5^(9/5.7) ≈ 9.5 mg (rounded to 9 mg) using the TrackCaffeine model; after 12 hours remaining = 28 × 0.5^(12/5.7) ≈ 7.0 mg (rounded to 7 mg) using the TrackCaffeine model (TrackCaffeine model arithmetic).

If a cup is consumed at 15:00, the calculation predicts roughly 19 mg remaining at 18:00, 13 mg remaining at 21:00, 9 mg remaining at 00:00, and 7 mg remaining at 03:00 after the single 28 mg dose, where those clock times and remaining amounts are computed with the TrackCaffeine first-order model (TrackCaffeine model, half-life 5.7 hours).

This single 28 mg cup represents 7% of the 400 mg daily guidance for healthy adults, where the 400 mg/day guidance is cited by the U.S. FDA and the percentage calculation (28 mg ÷ 400 mg = 0.07) uses the TrackCaffeine dataset value of 28 mg (U.S. FDA; TrackCaffeine dataset).

For people tracking caffeine relative to bedtime, a commonly used population finding is that large doses close to sleep reduce sleep duration; for example, Drake et al. 2013 reported that 400 mg taken six hours before bedtime reduced total sleep time by over an hour in a controlled study (Drake et al., 2013), and the 28 mg green tea dose is far smaller than 400 mg but will still follow the same elimination kinetics described above (TrackCaffeine model; Drake et al., 2013).

If targeting a 23:00 bedtime and using the TrackCaffeine half-life model, a 28 mg cup taken at 17:00 would leave approximately 13 mg at 23:00 according to remaining = 28 × 0.5^(6/5.7), where the half-life parameter is the TrackCaffeine population-average of 5.7 hours (TrackCaffeine model; TrackCaffeine dataset); you can explore personalized timing scenarios at our half-life calculator at caffeine half-life calculator (internal link to /tools/caffeine-calculator/) and check the last safe cup before bed using latest cup before bedtime (internal link to /tools/last-cup-before-bed/).

Certain populations should be more cautious: pregnant people are advised to limit caffeine to about 200 mg/day according to EFSA's 2015 opinion, where the 200 mg/day pregnancy guidance is from EFSA 2015 (EFSA, 2015), and adolescents and people with documented caffeine sensitivity should use lower targets such as those estimated by our safe daily limit by body weight tool (internal link to /tools/safe-daily-limit/; TrackCaffeine dataset).

Within the tea category this 28 mg green tea sits below the median: black and English Breakfast teas at 47–50 mg per 240 ml are roughly 1.7–1.8× higher than green tea, where the 47 mg and 50 mg values are from the TrackCaffeine dataset (TrackCaffeine dataset).

Compared with common caffeinated beverages outside tea, a 240 ml cup of drip coffee at 96 mg is about 3.4× the caffeine of this green tea cup, where the 96 mg drip coffee reference and 28 mg green tea value are both recorded in the TrackCaffeine dataset (TrackCaffeine dataset).

Other non-tea references in our dataset are useful context: a 355 ml Coke Zero contains 34 mg and a 250 ml Red Bull contains 80 mg, with those values listed in the TrackCaffeine dataset and showing that green tea at 28 mg is lower than many sodas and energy drinks in our data (TrackCaffeine dataset).

What changes the number for Green tea

Measured caffeine in green tea varies because brew strength, leaf type, steep time, and portion size change the extraction; this statement about sources of variation is supported by public food-composition studies (USDA FoodData Central).

Our dataset lists several same-category drinks for comparison: Black tea 47 mg per 240 ml, English Breakfast tea 50 mg per 240 ml, Earl Grey 47 mg per 240 ml, White tea 16 mg per 240 ml, Oolong 37 mg per 240 ml, Matcha (1 tsp) 70 mg per 240 ml, Chai latte 50 mg per 240 ml and Yerba mate 85 mg per 240 ml, where each value is taken from the TrackCaffeine dataset (TrackCaffeine dataset); a quick reference page for those items is available in our dataset hub at /dataset/ (internal link to /dataset/).

Practical reasons these numbers differ: leaf form (broken fannings versus whole-leaf) changes surface area and extraction rate (USDA FoodData Central), longer steep times generally increase caffeine extraction (USDA FoodData Central), and powdered preparations like matcha deliver substantially more caffeine because the whole leaf is consumed instead of an infusion (TrackCaffeine dataset).

For specific variants consider these examples from our categorized pages (TrackCaffeine dataset):

• Black tea — 47 mg per 240 ml as listed in our data (TrackCaffeine dataset).
• Matcha (1 tsp) — 70 mg per 240 ml because powdered whole-leaf consumption increases dose (TrackCaffeine dataset).
• White tea — 16 mg per 240 ml, representing a lower-caffeine brewed-leaf example in our data (TrackCaffeine dataset).

Decaffeinated green tea products exist and typically report minimal remaining caffeine, but specific decaf numbers are brand-dependent and should be checked on product labelling or in authoritative databases such as USDA FoodData Central (USDA FoodData Central).

Where this figure comes from

The 28 mg figure on this page is taken from the TrackCaffeine dataset aggregation for green tea brewed to a 240 ml serving size (TrackCaffeine dataset), with cross-reference to public food composition entries such as USDA FoodData Central where available (USDA FoodData Central).

Published values differ because laboratory assays, steep times, leaf cultivar, and portion definitions vary between sources; any new peer-reviewed chemical analysis or authoritative database update (for example an updated USDA FoodData Central entry) would prompt a change to the listed value (USDA FoodData Central; TrackCaffeine dataset).

Bottom line

Bottom line: one 240 ml cup of green tea contains 28 mg of caffeine (TrackCaffeine dataset), which equals 11.7 mg per 100 ml (TrackCaffeine dataset), is about 0.3× a 240 ml drip coffee at 96 mg (TrackCaffeine dataset), and is 7% of the 400 mg/day guidance for healthy adults (U.S. FDA).

Under a first-order elimination model with a population-average half-life of 5.7 hours (TrackCaffeine model), that 28 mg decays to roughly 19 mg after 3 hours, 13 mg after 6 hours, 9 mg after 9 hours, and 7 mg after 12 hours (TrackCaffeine model arithmetic).