Tea cultivar, leaf grade, growing conditions, water temperature, and brewing time can all affect how much caffeine is extracted into your cup. Research has shown that brewing conditions can substantially change the caffeine and L-theanine content of a tea infusion.
So, think of the numbers below as a reference, not a fixed rule.
Typical Caffeine Content in Tea
| Tea Type | Typical Caffeine Reference |
|---|---|
| Green Tea | ~20–45 mg / 240 mL cup |
| Black Tea | ~30–60 mg / 240 mL cup |
| Oolong Tea | ~20–50 mg / 240 mL cup |
| Matcha | ~40–70 mg / 2 g serving |
These are approximate ranges. Actual caffeine content can vary depending on the tea, amount used, and brewing method.
Your Brewing Method Matters
The amount of caffeine you drink is closely connected to how much tea leaf you use and how you brew it.
For example, using more leaves generally gives you more compounds to extract. A longer brewing time or higher water temperature can also change the amount of caffeine that moves from the leaf into your cup.
This is especially important with oolong tea.
A traditional small-pot or gaiwan brewing style may use a relatively large amount of tea leaves, but each infusion is small and often brewed for a short time. You may drink several infusions, rather than one large 240 mL cup.
So comparing:
"One cup of oolong" vs. "one cup of coffee"
isn't always an apples-to-apples comparison.
Your actual caffeine intake depends on the leaves, the amount you use, and how much of the brewed tea you drink.
What Makes Tea Different From Coffee?
Tea contains caffeine, but it also naturally contains L-theanine, an amino acid found in tea leaves.
Scientists have been interested in whether these two compounds may work together.
A 2025 systematic review and meta-analysis published in Nutrition Reviews examined randomized controlled trials investigating tea, L-theanine, caffeine, and combinations of L-theanine with caffeine. The review found evidence that the combination may improve certain measures of attention and alertness, although the effects varied across studies and more research is needed.
Importantly, many of the studies used isolated L-theanine and caffeine rather than ordinary cups of tea.
This means we shouldn't think of tea simply as "caffeine with a calming ingredient."
Instead, tea offers a naturally complex combination of compounds — and that combination may be one reason drinking tea can feel different from drinking coffee.
A Note About Caffeine
If You're Sensitive to Caffeine
Remember that oolong tea is still a caffeinated drink. The fact that tea may feel gentler than coffee does not mean it is caffeine-free, nor does L-theanine eliminate caffeine's effects.
The best way to understand your own cup is to pay attention to the tea you're using and your brewing method.
More leaves. More time. Different temperature. Different cup.
That's part of the beauty of tea: there is no single number that tells the whole story.
References
- Nutrition Reviews (2025). "Effects of Tea or its Bioactive Compounds l-Theanine or l-Theanine plus Caffeine on Cognition, Sleep, and Mood: A Systematic Review and Meta-Analysis." https://academic.oup.com/nutritionreviews/article/83/10/1873/8123998
- Tea composition and brewing conditions research examining caffeine and L-theanine levels in tea infusions across different brewing variables.