As a general rule, coffee contains more caffeine than tea; however, the amount of caffeine in tea and coffee depends on the brand and type in question. Brewed coffee contains between 95 and 200 mg of caffeine for a quantity of 8 fluid ounces, while the same quantity of black tea contains only 14 to 70 mg.
When tea and coffee are decaffeinated, the quantity of caffeine is greatly reduced but not always eliminated totally. A quantity of 8 fluid ounces of brewed decaffeinated coffee contains between 2 and 12 mg of caffeine while the same quantity of black decaffeinated tea contains between 0 and 12 mg. Teas other than black tea contain caffeine, and the amount varies depending on the brand, the type and also on the brewing method. Green tea contains between 7.6 and 47.8 mg, while oolong tea contains 12 to 55 mg. White tea contains between 6 and 25 mg. Espresso coffee contains a greater amount of caffeine per fluid ounce; however, as it is generally drunk in much smaller quantities than ordinary brewed coffee, its caffeine content can be less. Instant coffee contains between 27 and 173 mg of caffeine, and the decaffeinating process reduces this to between 2 and 12 mg.