While 1kg of tea leaves contains more caffeine than 1kg of coffee beans, a tea infusion contains less caffeine than a cup of coffee.
Furthermore, there are huge differences in the caffeine content of different types of tea and the caffeine content can be reduced or increased depending on the infusion time.
According to research, the Japanese green teas such as Matcha, Sencha and Gyokuro have the highest caffeine content - more than 100 mg for 250 ml for Matcha! Among teas with the lowest caffeine content - less than 20 mg for 250 ml - there are many oolong teas, in the following order:
Dong Ding oolong tea (from Taiwan) - 20 mg of caffeine for 250 ml of tea
Tie Guan Yin or Iron Goddess of Mercy (from Fujian in China) - 17 mg of caffeine for 250 ml of tea
Mi Lan Xiang oolong tea and Rou Gui oolong tea - 16 mg of caffeine for 250 ml of tea