A standard 8-ounce cup of brewed black tea contains about 47 to 48 mg of caffeine, roughly half the amount in the same size cup of coffee. That number can swing anywhere from 25 to 70 mg depending on the tea variety, how you brew it, and whether you’re using tea bags or loose leaves.
What Changes the Caffeine in Your Cup
The 47–48 mg average is useful as a baseline, but the actual caffeine you get is shaped by several factors working together. The biggest levers are water temperature, steeping time, and leaf size.
Water temperature has a dramatic effect. Research published by the American Chemical Society measured caffeine extraction at three temperatures and found stark differences. Tea steeped at boiling (100°C) for six minutes yielded about 47 mg per 8-ounce cup. The same tea steeped at 50°C (roughly 120°F) for the same time produced only about 30 mg. At room temperature, it dropped to around 14 mg. In other words, the hotter your water, the more caffeine ends up in your cup.
Steeping time matters too, but with diminishing returns. At boiling temperature, one minute of steeping extracted roughly 25 mg, while four minutes pulled out about 43 mg. After six minutes the caffeine concentration plateaued and even dipped slightly, suggesting most of the available caffeine had already dissolved.
Tea Bags vs. Loose Leaf
Tea bags generally deliver more caffeine than loose leaf tea, especially on the first brew. The reason is surface area. Tea bags are typically filled with finely ground leaf particles (called dust and fannings in the tea industry), which expose far more of the leaf’s interior to water. Whole loose leaves release their caffeine more gradually, so the same steeping time often yields a milder cup. If you’re trying to limit caffeine, loose leaf brewed for a shorter time is the simplest way to bring the number down.
How Caffeine Varies by Tea Variety
Not all black teas start with the same caffeine content. The tea plant has two main varieties. The Assam variety, grown widely in India, Sri Lanka, and parts of Africa, naturally contains more caffeine than the Chinese variety used in many traditional Chinese black teas. Assam teas are also often processed into smaller, broken-leaf grades that extract quickly, compounding the effect. A strong cup of Assam can push toward 60–70 mg, while a lighter Darjeeling or Chinese black tea might sit closer to 40 mg.
The USDA average of about 47 mg reflects a blend of these sources, so treat it as a midpoint rather than a guarantee for any specific tea you buy.
Black Tea vs. Coffee and Other Drinks
According to Mayo Clinic data, an 8-ounce cup of brewed coffee delivers about 96 mg of caffeine, almost exactly double the 48 mg in the same size serving of black tea. That makes black tea a natural choice if you want a moderate caffeine boost without the intensity of coffee. For context, here’s how black tea stacks up:
- Brewed coffee (8 oz): ~96 mg
- Black tea (8 oz): ~47–48 mg
- Green tea (8 oz): ~25–30 mg
- Decaffeinated black tea (8 oz): less than 4 mg
If you drink tea specifically to avoid caffeine, decaf black tea still contains trace amounts, typically under 4 mg per cup. The decaffeination process removes most but not all caffeine, so it’s not truly zero.
How Many Cups You Can Safely Drink
The FDA considers up to 400 mg of caffeine per day safe for most healthy adults, a threshold confirmed by a 2017 systematic review. At roughly 48 mg per cup, that works out to about 8 cups of black tea before you’d hit that ceiling. Most people drink far less than that. Even three or four cups a day keeps you well within the safe range, with room for other caffeine sources like chocolate or soda.
Pregnant individuals, people sensitive to caffeine, and those on certain medications may need to aim lower. Sensitivity varies widely: some people feel jittery after two cups of tea, while others notice nothing after four. Your own response is a better guide than any universal number.
Practical Ways to Control Your Intake
If you want more caffeine from your tea, use boiling water, steep for five to six minutes, and choose an Assam or breakfast blend in tea bag form. If you want less, try loose leaf tea, steep for two to three minutes, and use water that’s slightly below boiling. Switching to a lighter Chinese-style black tea also helps. These adjustments can easily shift your cup from 25 mg on the low end to 60–70 mg on the high end, giving you a surprising amount of control over what you’re actually drinking.