Tea contains caffeine — the same compound found in coffee. Wikipedia's caffeine article notes that tea leaves and coffee beans are the most common sources of caffeine for people.
How much ends up in your cup depends on the tea and how you brew it. Here are published figures from reliable sources.
- Black tea: about 50 mg per 220 ml cup (healthdirect)
- USDA, per 240 ml: black 47 mg, oolong 38 mg, green 29 mg
- Healthy adults: around 400 mg a day
- Pregnant or breastfeeding: 200 mg a day
- Most herbal teas: caffeine-free
How much caffeine is in a cup?
healthdirect Australia lists about 50 mg of caffeine in a 220 ml cup of black tea.
Wikipedia's white tea article quotes US Department of Agriculture figures for an 8 fl oz (240 ml) cup:
| Tea (240 ml cup) | Caffeine (USDA) |
|---|---|
| Black tea | 47 mg |
| Oolong tea | about 38 mg |
| Green tea | about 29 mg |
| White tea | estimates range widely, from under 10 mg to over 50 mg |
The same article notes that because caffeine content varies so much, some studies have failed to find a clear relationship between the type of tea and its caffeine content.
What affects caffeine content?
Wikipedia's caffeine article notes that preparation and many other factors have a significant impact, and that colour is a poor indicator of caffeine. For example, the pale Japanese green tea gyokuro contains far more caffeine than much darker teas such as lapsang souchong.
The sencha article adds that higher water temperatures extract more caffeine, and that brewing temperature, time and tea-to-water ratio all matter.
How much is too much?
healthdirect Australia states:
- "Healthy adults can safely have around 400 mg of caffeine a day."
- If you are pregnant or breastfeeding, it's a good idea to limit caffeine to 200 mg per day.
Caffeine-free options
According to Wikipedia's article on herbal tea, most herbal infusions do not naturally contain caffeine — though a few, such as yerba mate and guayusa, do. Popular caffeine-free choices include hibiscus, rooibos, chamomile and peppermint. See Caffeine-Free Teas for the Evening.
Note that flavoured teas built on black tea — such as Earl Grey or many cinnamon and cardamom teas — still contain caffeine. Check the ingredients.
"Theine" is caffeine
You may see the word "theine". Wikipedia's caffeine article records that in 1838 it was shown that theine, isolated from tea, is actually the same substance as caffeine.
Sources & further reading
- healthdirect Australia: Caffeine
- Wikipedia: Caffeine
- Wikipedia: White tea (USDA caffeine figures)
- Wikipedia: Sencha
- Wikipedia: Herbal tea
