There is no simple answer to the question- “How much caffeine is in my cup of tea?” Many variables can affect the level of caffeine in a cup of brewed tea. Even the location of the individual tea plant can have an effect on caffeine levels! Once picked, the tea leaves can be processed in many different ways, resulting in different types of teas (Black, Green, White, etc.) with differing levels of caffeine. Every step of the brewing process, from water temperature to length of brewing time and water/tea ratios can affect the caffeine levels. Pinpointing the amount of caffeine in a cup of tea is a wildly unpredictable proposition!
While a precise caffeine measurement in each cup is nearly impossible, we can get a rough estimate of the amount of caffeine in the tea we are drinking. First, remember that all ‘traditional’ teas come from leaves of the exact same plant- the Camellia sinensis. Therefore, all ‘traditional’ teas will contain caffeine. Leaves from the tea plant are picked, then processed in very different ways—some dried, some compressed and fermented, some rolled. The processing method has the most significant effect on the level of caffeine. As a general rule, brewed Black teas have the highest caffeine level, with 60-75 mg of caffeine in an 8 oz cup. Oolong tea is slightly lower with 30-45 mg of caffeine in one cup, followed by Green tea (15-30 mg) and finally, White tea (10-15 mg).
Other factors can contribute to tea caffeine level. The length of brewing time can certainly affect the caffeine in your cup. It would stand to reason that the longer you steep your tea, the more caffeine will end up in your cup! The quality and shape of the tea leaves can change things, as well. The more broken up your tea leaves are, the more caffeine they will release into the water. In other words, tea made from tea bags, as opposed to loose leaf teas, can have a higher concentration of caffeine!
If you can’t or won’t have caffeine, you don’t have to be left out! While caffeine can’t be avoided with most ‘traditional’ teas, Herbal teas and Tisanes (dried fruit teas) do not contain any actual tea leaves, and therefore are entirely caffeine-free. Rooibos teas are caffeine-free as well. These teas are excellent choices for the caffeine conscious, or perhaps in the evening time.