Red Bull has more caffeine than brewed black tea on both counts: 80mg per 8.4 oz can against 47mg per 8 oz cup, and about 10mg per fluid ounce against 6. The serving sizes differ, so the table below shows both ways of counting.
These are different categories of drink, which changes how the caffeine arrives. Energy drinks and sodas list an exact number because caffeine is a measured additive; brewed drinks vary with the beans and the brew, so their figures are compiled averages. The numbers here are the standard published values for each.
brewed black tea vs Red Bull: the numbers
| brewed black tea | Red Bull | |
|---|---|---|
| Caffeine per serving | 47mg per 8 oz cup | 80mg per 8.4 oz can |
| Caffeine per fl oz | 5.9mg | 9.5mg |
| Servings to reach 400mg (FDA context) | 8.5 | 5.0 |
Sources: brewed black tea's figure is verified in our brewed black tea caffeine guide against USDA FoodData Central (source); Red Bull's figure is verified in our Red Bull guide against Red Bull label / Caffeine Informer (source).
Which one should you pick?
Pick brewed black tea when you want the lighter dose or a slower ramp, and Red Bull when you actually need the bigger hit and know your tolerance. If you are stacking either with other caffeinated drinks through the day, run the math against the 400mg reference rather than guessing.
For context, the FDA cites 400mg of caffeine a day as an amount generally not associated with negative effects in healthy adults. Tolerance and health vary, so treat these numbers as information, not advice.
Related reading
- brewed black tea: the full caffeine guide
- Red Bull: the full caffeine guide
- The verified caffeine database
FAQ
Does brewed black tea or Red Bull have more caffeine? Red Bull: 80mg per 8.4 oz can versus 47mg per 8 oz cup for brewed black tea.
Which is stronger per ounce? Red Bull, at about 9.5mg per fluid ounce versus 5.9mg for brewed black tea.
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