A moderate dose that scales with cup size and steep time
Black tea is brewed from the leaves of Camellia sinensis, the same plant as green, white and oolong teas. The USDA FoodData Central entry for black tea brewed with tap water lists 47 mg of caffeine in an 8 oz cup and 36 mg in a 6 oz cup. The actual value in your cup can range higher or lower depending on how long the leaves steep and how much leaf is used.
Longer steeping extracts more caffeine. A breakfast tea steeped for three minutes may be close to the USDA figure; a strong tea left for five minutes can exceed it. The type of leaf matters less than the steep time and the amount of water.
Comparing to coffee and energy drinks
An 8 oz black tea at 47 mg is about half the caffeine of an 8 oz brewed coffee at 95 mg and slightly more than an 8 oz green tea at roughly 28 mg. It is far less than a 12 oz energy drink. For people reducing caffeine but not eliminating it, black tea is a useful intermediate step.
Because the dose is moderate, black tea is less likely to disrupt sleep than coffee when consumed at the same time. Individual metabolism still varies, so sensitive people may need an earlier cutoff.
Why the numbers vary so much
Published caffeine values for black tea vary from 25 mg to 90 mg per 8 oz cup, depending on the source and preparation. The USDA figure of 47 mg is a benchmark for standard brewing, but a teabag left in the cup for five or more minutes can produce 70 mg or more. If you are tracking caffeine precisely, use the USDA figure as a baseline and increase it for stronger brews.
Source
The caffeine figures are from USDA FoodData Central, black tea brewed with tap water, checked 19 September 2026.