A standard 8-ounce cup of brewed black tea contains about 48 mg of caffeine. That’s roughly half what you’d get from the same size cup of coffee, but the actual number in your mug can vary quite a bit depending on how you brew it, what type of tea you use, and how long you let it steep.
How Brewing Changes the Caffeine
The two biggest variables you control are water temperature and steeping time, and both make a dramatic difference. Research published by the American Chemical Society measured caffeine extraction from tea at different temperatures and intervals, and the numbers tell a clear story.
With boiling water (212°F / 100°C), a one-minute steep yields about 25 mg of caffeine per 8-ounce cup. By four minutes, that climbs to around 43 mg, and it peaks near 47 mg at six minutes before leveling off. Drop the water temperature to roughly 120°F (50°C), and those numbers shrink considerably: a four-minute steep at that temperature only extracts about 24 mg, nearly half the amount you’d get with boiling water at the same time. At room temperature, even an eight-minute steep pulls out only about 17 mg.
The practical takeaway: if you want less caffeine, use slightly cooler water and steep for a shorter time. If you want more, use a rolling boil and let it sit for four to six minutes. Going beyond six minutes doesn’t meaningfully increase caffeine and tends to make the tea bitter.
Tea Bags vs. Loose Leaf
Tea bags generally release caffeine faster than loose leaf tea because the leaves inside are broken into smaller pieces, giving hot water more surface area to work with. Whole loose leaves extract caffeine more slowly, so a short steep with loose leaf tea will typically deliver less caffeine than the same steep with a standard tea bag. Over a longer brew time, the difference narrows. If you’re using a tea bag and steeping for three to five minutes in boiling water, you’re likely getting the full 40 to 50 mg range.
Caffeine by Tea Variety
Not all black teas start with the same amount of caffeine in the leaf. The tea plant has two main varieties, and the one grown widely in India, Sri Lanka, and parts of Africa (the Assam variety) tends to contain more caffeine than the variety common in China. That means an Assam or Ceylon black tea will generally deliver a stronger caffeine hit than a Chinese black tea like Keemun, even when brewed identically.
Darjeeling is an interesting case. It’s grown from the Chinese variety of the plant but cultivated in India, and it typically falls on the lower end of the black tea caffeine range. If you’re caffeine-sensitive but still want black tea, Darjeeling or other Chinese-variety teas are a reasonable choice.
Black Tea vs. Coffee and Green Tea
For context, an 8-ounce cup of brewed coffee contains roughly 95 mg of caffeine, about double what black tea delivers. Green tea sits lower, typically in the 25 to 30 mg range per cup. So black tea lands squarely in the middle: enough to provide a noticeable lift, but far less likely to cause jitteriness or sleep disruption than coffee.
This middle ground is one reason people switch from coffee to black tea when they want to cut back on caffeine without giving it up entirely. Three cups of black tea across a day gives you roughly 140 to 150 mg, well under the 400 mg daily limit the FDA considers safe for most adults, and about what you’d get from a single large coffee.
What About Decaf Black Tea?
Decaffeinated black tea still contains a small amount of caffeine. Most decaf teas retain about 1 to 2 percent of the original caffeine, which works out to roughly 2 mg or less per cup. For most people, that’s negligible. However, regulation around “decaf” labeling isn’t strict, and some products may contain more than expected. If you’re highly sensitive to caffeine or avoiding it for medical reasons, it’s worth knowing that decaf doesn’t mean zero.
How Many Cups You Can Drink
At about 48 mg per cup, you could drink eight cups of black tea before hitting the FDA’s 400 mg daily guideline. Most people drink two to four cups a day and stay well within that range. Keep in mind that your total caffeine intake includes everything you consume: chocolate, soda, energy drinks, and any coffee you drink alongside your tea all count toward that number.
Caffeine sensitivity varies from person to person based on genetics, body weight, and how regularly you consume it. If a single cup of black tea in the afternoon keeps you up at night, that’s your body’s signal to set an earlier cutoff time, regardless of what the general guidelines say. Caffeine’s effects typically peak about 30 to 60 minutes after you drink it and take four to six hours to drop by half in your system.