How much caffeine is in tea?
About 47 mg in an 8 oz cup of brewed black tea and about 29 mg in a cup of brewed green tea, by the USDA’s numbers. That’s half of an 8 oz coffee or less, which has about 95 mg.
People who switch to tea in the afternoon often think they’ve switched to nothing, and people who drink tea all day often think they barely have any caffeine. Both are a bit off. A black tea is half a coffee, and two of them make a whole one.
We’d make tea your afternoon drink if coffee keeps you up. A black tea at 5pm leaves about 23 mg at an 11pm bedtime, less than a can of Coke starts with. A green tea at the same time leaves about 14. It’s the easiest swap on the menu, since you keep a hot cup and lose half the dose or more.
Tea against coffee
The USDA measures brewed black tea at 20 mg of caffeine per 100 g and brewed coffee at 40, so cup for cup, black tea has half.
| Drink | Caffeine | Left at 11pm from a 3pm cup | Left at 11pm from a 7pm cup |
|---|---|---|---|
| Green tea, 1 cup | 29 mg | 11 mg | 18 mg |
| Black tea, 8 oz | 47 mg | 17 mg | 30 mg |
| Matcha, 2 g of powder | about 32 to 84 mg | about 12 to 31 mg | about 20 to 54 mg |
| Brewed coffee, 8 oz | 95 mg | 35 mg | 60 mg |
These use the average half-life of 5 hours. A tea bag left in for a long time, or two bags in one mug, will be stronger than the USDA’s cup.
Two teas make a coffee
A black tea at 3pm and another at 5pm leave about 40 mg in you at 11pm. One 8 oz coffee at 4pm leaves the same. The afternoon pot is fine, as long as you count it like the coffee it adds up to.
Matcha is the exception. You drink the whole ground leaf, so a strong serving can come close to a coffee (caffeine in matcha).
How late can you have tea?
For an 11pm bedtime, a black or green tea fits as late as 7pm, four hours before bed. In a 2025 trial, 100 mg taken 4 hours before bed did nothing measurable to sleep, and a cup of tea is half that dose. None of the trials tested a small dose closer to bedtime than 4 hours, so we stop there.
Try your own afternoon in the cutoff clock below. The drinks tool has every tea and coffee side by side, to scale.
47 mg
Black tea, 8 oz. USDA FoodData Central 173227: 20 mg per 100 g. One at 3pm still leaves about 17 mg at an 11pm bedtime.
When should I stop?
When you fall asleep at 11:00pm
83 mgA measured cost
You'll fall asleep with about a cup of coffee in you.
- Brewed coffee, 8 oz95 mg
Brewed coffee, 16 oz190 mg
Your last drink, a 16 oz coffee at 3:00pm
- Under 40 mg at sleep
- by 8:10am
- Under 80 mg
- by 2:45pm
The full clock, with the band, 3am and the table by drink.
6 sources
- USDA FoodData Central, SR Legacy: brewed coffee (171890), espresso (171891), brewed black tea (173227) and brewed green tea (171917)fdc.nal.usda.gov
- Gardiner C and others, Dose and timing effects of caffeine on subsequent sleep: a randomized clinical crossover trial, Sleep, 2025doi.org
- The Coca-Cola Company, What is caffeine?coca-colacompany.com
- Koláčková T and others, Antioxidants, 2022 (16.1 mg of caffeine per gram of matcha)doi.org
- Mashaqbeh ET and others, PLOS ONE, 2026 (41.8 mg of caffeine per gram of matcha)doi.org
- Antonio J and others, Common questions and misconceptions about caffeine supplementation: what does the scientific evidence really show? Journal of the International Society of Sports Nutrition, 2024doi.org
