The caffeine content varies with each tea based on the type, where it is grown, how it is processed, exposure to heat, brewing time, water temperature and number of infusions. Dry tea can have more caffeine than dry coffee by weight due to the difference in yield. Brewed tea typically has one-third the caffeine content of brewed coffee, depending on the preparation methods.

Herbal infusions do not have any caffeine at all. Decaffeinated teas have approximately .4% of caffeine as measured by dry weight analysis. Generally, this yields 3 to 4 mg. per cup of brewed tea. Green tea has less caffeine than black tea due to the processing methodology, the use of lower water temperature and a shorter optimal brewing time.