Green tea vs Black tea: caffeine compared
Black tea (8 oz) has 47 mg of caffeine, 19 mg more than Green tea (8 oz, 28 mg) — 1.7× as much per serving. Per fluid ounce, Black tea is the stronger drink: 5.9 mg/oz versus 3.5 mg/oz.
| Green tea | Black tea | |
|---|---|---|
| Serving | 8 oz | 8 oz |
| Caffeine per serving | 28 mg | 47 mg |
| Per fl oz | 3.5 mg | 5.9 mg |
| Share of 400 mg/day | 7% | 12% |
| Servings to reach 400 mg | 14.3 | 8.5 |
| Hours until under 50 mg | already under | already under |
| Last one for an 11 PM bedtime · standard (50 mg) | 11:00 PM | 11:00 PM |
| Last one for an 11 PM bedtime · sensitive (25 mg) | 10:11 PM | 6:27 PM |
| Share of the 200 mg pregnancy limit | 14% | 24% |
One serving of each, over 16 hours
Common questions
Which has more caffeine, Green tea or Black tea?
Black tea (8 oz) has about 47 mg versus 28 mg in Green tea (8 oz): 19 mg more, or 1.7× as much.
Which is stronger per ounce, Green tea or Black tea?
Black tea: about 5.9 mg per fl oz versus 3.5 mg for Green tea. Serving size decides the total you actually drink.
How many Green tea servings equal one Black tea?
About 1.7 servings of Green tea (8 oz) match the caffeine in one Black tea (8 oz).
When should I stop drinking Green tea or Black tea before bed?
For an 11 PM bedtime with a 50 mg limit and a 5-hour half-life: last Green tea by 11:00 PM, last Black tea by 11:00 PM. Half-life varies from about 1.5 to 9.5 hours between people.
Method
Caffeine per labeled serving, from the same drink table every calculator here uses (FDA/USDA reference amounts and manufacturer labels; see caffeine content of every drink). Brewed drinks vary batch to batch, so read these as typical values. Decay uses a 5-hour average half-life with a 45-minute absorption ramp; cutoff = bedtime − 5 h × log₂(dose ÷ limit). Percentages use the FDA's 400 mg/day figure for healthy adults and the 200 mg/day limit ACOG gives for pregnancy.
Source — Green tea: USDA FoodData Central (SR Legacy 171917), checked 2026-10-13. 12 mg per 100 g × 237 g.
Source — Black tea: USDA FoodData Central (SR Legacy 173227), checked 2026-10-13. 20 mg per 100 g × 237 g.