A cup of green tea has close to 28 milligrams (mg) of caffeine, which places it marginally powering black tea’s 47 mg, in accordance with the Mayo Clinic. On the other hand, there could be plenty of variation in caffeine content based upon how tea is processed and brewed. https://www.goteaworld.com/arizona-green-tea-is-it-good-for-you-5-facts/