Because the caffeine content in green tea exists on a spectrum, the U.S. FDA estimates an 8-ounce cup of green tea can contain anywhere from 30 to 50 mg of caffeine.

In unprocessed form, tea leaves contain 3.5% caffeine, while coffee beans contain between 1 and 2.2% — so by that metric, you would actually expect tea to be more caffeinated than coffee.

Because the caffeine content in green tea exists on a spectrum, the U.S. FDA estimates an 8-ounce cup of green tea can contain anywhere from 30 to 50 mg of caffeine.

The longer tea is steeped, the more caffeine that’s extracted from the tea leaves or buds. Studies show that steeping tea for over 7–10 minutes significantly increases its caffeine content.

While black tea has less caffeine than coffee, it’s still a caffeinated beverage. Black tea has about 47 milligrams of caffeine while a cup of joe comes in at just under 100 milligrams of caffeine.

Hot water draws more caffeine out of tea leaves in a shorter period of time, and the same holds for coffee. Coffee is typically brewed at a temperature of about 195 to 205°F (90 to 96°C).