How much caffeine is in Oolong tea?
of caffeine
Source: public manufacturer data and USDA FoodData Central. Values are estimates, not exact or medical measurements.
- 37 mg of caffeine per 240 ml (8.1 fl oz) serving (15.4 mg per 100 ml).
- About 0.4 cups of brewed coffee, and 9% of the FDA's 400 mg daily limit for healthy adults.
- After 6 hours roughly 18 mg is still in your system; after 12 hours about 9 mg.
- To stay under the 100 mg many people notice at bedtime, finish it about 0 h before sleep.
Oolong tea delivers about 37 mg of caffeine per 240 ml (8.1 fl oz) serving, the equivalent of roughly 0.4 cups of brewed coffee (a 240 ml cup is about 96 mg). That is about 59 mg less caffeine than a standard cup of coffee.
At 15.4 mg per 100 ml, Oolong tea is mild by concentration — the fair way to compare it against drinks of a different size.
How long Oolong tea stays in your system
Caffeine leaves the body through first-order elimination with a population-average half-life of about 5.7 hours. Starting from 37 mg, roughly 26 mg is left after 3 hours, about 18 mg after 6 hours, and around 9 mg after 12 hours. Your personal rate varies — smoking speeds it up, pregnancy and some medications slow it down — which is why the calculator below lets you set your own half-life and bedtime.
Oolong tea and your daily limit
For most healthy adults the FDA points to about 400 mg of caffeine a day as an amount not generally linked to negative effects. One serving of Oolong tea is 9% of that ceiling. Pregnant people are usually advised to stay under about 200 mg a day, and the American Academy of Pediatrics discourages caffeine for children and adolescents. This is general guidance, not medical advice. The easiest way to stay under your own limit is to log every drink — CoffeeLog adds up your real daily total automatically.
How long it stays in your system
Starting from one serving, here is roughly how much caffeine is left as the hours pass (population-average half-life of 5.7 hours).
| Time | Caffeine left | % left |
|---|---|---|
| At serving | 37 mg | 100% |
| After 1 h | 33 mg | 89% |
| After 3 h | 26 mg | 70% |
| After 6 h | 18 mg | 49% |
| After 9 h | 12 mg | 32% |
| After 12 h | 9 mg | 24% |
Your personal caffeine curve
Estimates for general information, not medical advice.
How it compares
| Drink | Serving | Caffeine |
|---|---|---|
| Oolong tea | 240 ml | 37 mg |
| Yerba mate | 240 ml | 85 mg |
| Matcha (1 tsp) | 240 ml | 70 mg |
| English Breakfast tea | 240 ml | 50 mg |
| Chai latte | 240 ml | 50 mg |
| Black tea | 240 ml | 47 mg |
| Earl Grey tea | 240 ml | 47 mg |
Frequently asked questions
How much caffeine is in Oolong tea?
Oolong tea contains about 37 mg of caffeine per 240 ml (8.1 fl oz) serving (15.4 mg per 100 ml). Values are public-source estimates, not exact measurements.
Is 37 mg of caffeine a lot?
It is about 0.4 cups of brewed coffee. The FDA considers up to 400 mg per day safe for most healthy adults, so this is a moderate single dose.
How long does the caffeine in Oolong tea stay in your system?
Caffeine has a half-life of about 5.7 hours, so roughly 26 mg of the original 37 mg remains after 3 hours and about 9 mg after 12 hours. The calculator above shows your personal curve.
Will Oolong tea keep you awake?
It can if you have it late. From 37 mg it takes roughly 0 hours to fall below the 100 mg level many people notice at bedtime. Finish it well before sleep, or use the cutoff above.
Track this automatically with CoffeeLog
Log any drink in one tap, watch caffeine fade in real time on your home screen, and get a nudge before it touches your sleep — the same engine that powers this page.
Related
TrackCaffeine provides general reference information about caffeine. It is not medical advice. Caffeine values are public-source estimates, not exact measurements.