A standard 8-ounce cup of brewed black tea contains roughly 40 to 90 milligrams of caffeine, with 48 mg being a common midpoint. That’s a wide range, and where your cup falls depends on the tea variety, how hot your water is, and how long you let it steep.
Caffeine by Tea Variety
Not all black teas are created equal. Assam tea, grown in India’s lowland river valleys, tends to be on the stronger end at 60 to 90 mg per 8-ounce cup. Darjeeling, grown at higher elevations, is lighter and comes in at 40 to 70 mg. These differences come down to the plant cultivar, growing conditions, and how the leaves are processed.
Flavored black teas like Earl Grey generally contain less caffeine than unflavored varieties. Twinings lists its unflavored black teas at 40 to 76 mg per serving, while its flavored black teas come in at 31 to 45 mg. The added bergamot oil or other flavorings don’t reduce caffeine directly, but flavored blends often use a lighter tea base or include non-tea ingredients that dilute the overall caffeine per bag.
How Steeping Changes Your Caffeine
The longer tea sits in hot water, the more caffeine it releases. Research measuring caffeine extraction over time found that after 1 minute of steeping, only about 18% of the available caffeine has dissolved into the water. At 3 minutes, that jumps to 48%. By 5 minutes, you’re getting roughly 69% of the total caffeine. If you steep for a full 10 minutes, about 92% has been extracted. So a quick dunk gives you a noticeably milder cup than a long, leisurely steep.
Water temperature matters just as much. A study published in the Journal of Chemical Education tracked caffeine release at three temperatures and found dramatic differences. After 4 minutes of steeping, tea brewed at boiling (100°C) yielded about 43 mg per 8-ounce cup. The same tea at 50°C produced only 24 mg, and at room temperature (20°C), just 10 mg. If you accidentally pour water that’s cooled down significantly before it hits your tea bag, you’ll get a much weaker caffeine hit than you might expect. For maximum extraction, use fully boiling water.
Black Tea vs. Coffee
Black tea delivers roughly half the caffeine of brewed coffee, sometimes less. A standard 8-ounce cup of drip coffee contains about 95 mg of caffeine, compared to black tea’s 40 to 90 mg range. In practice, most people’s cup of black tea lands closer to 50 mg, making it a solid option if you want a moderate energy boost without the intensity of coffee. Your body processes the caffeine identically regardless of the source, so the difference is purely about dose.
Decaf Black Tea Still Has Some Caffeine
Decaffeinated black tea isn’t completely caffeine-free. Most decaf black teas contain fewer than 4 mg per cup. That’s a tiny amount (about the same as a few bites of dark chocolate), but it’s worth knowing if you’re avoiding caffeine entirely for medical reasons or late-night drinking.
How Many Cups You Can Safely Drink
The FDA sets the general guideline for healthy adults at 400 mg of caffeine per day. At roughly 50 mg per cup, that translates to about 8 cups of black tea before you’d hit that ceiling. Even heavy tea drinkers rarely approach this limit from tea alone, but caffeine adds up across your entire diet: coffee, soda, energy drinks, chocolate, and some medications all contribute. Going past 400 mg can cause jitteriness, insomnia, an elevated heart rate, nausea, and anxiety. Toxic effects like seizures are associated with rapid intake of around 1,200 mg, but that’s essentially impossible to reach through brewed tea.
Getting a Consistent Cup
If you want to control your caffeine intake more precisely, the two biggest levers are steep time and water temperature. Use boiling water and steep for 3 to 5 minutes for a standard-strength cup in the 40 to 50 mg range. Cutting your steep time to 1 minute drops the caffeine by more than half. Using cooler water (say, from a kettle that’s been sitting for several minutes) can cut it further.
Loose-leaf tea and tea bags can also differ. Tea bags often contain smaller, broken leaf particles called “fannings” that release caffeine faster than whole loose leaves, so a 3-minute steep with a bag may yield more caffeine than 3 minutes with loose leaf. If you’re switching between the two, expect a slight shift in strength even with identical timing.