An 8-ounce (about 240 ml) cup of green tea typically contains between 30 and 50 milligrams of caffeine

. This amount is lower than that found in black tea and considerably less than in coffee, which usually contains 80 to 100 milligrams per 8-ounce cup

. The caffeine content in green tea can vary depending on factors such as the type of tea leaves, how the tea is brewed (temperature and steeping time), and whether the tea is bagged or loose leaf, with bagged teas generally having slightly more caffeine

. For example, some varieties like Chinese Mao Feng green tea can have higher caffeine levels, around 115 mg per serving, and Indian Darjeeling green tea around 96 mg, showing that caffeine content can vary widely depending on the variety

. In summary, a standard cup of green tea has about 30-50 mg of caffeine, but this can fluctuate based on tea type and preparation methods