tea by caffeine
On average, a cup of tea contains 1/2 to 1/3 as much caffeine as a cup of coffee. The actual tea leaf has more caffeine than coffee in raw form but because coffee is dissolved in the cup and tea is only infused (the leaf does not dissolve at all) much less caffeine is transfered to the brew.
Black tea generally contains approximately 40 - 50 mg of caffeine per cup.
Green tea generally contains about 20 - 25 mg of caffeine per cup. Green tea's caffeine is thought to be absorbed more slowly into the body so it tends to not give as much of a buzz; rather a prolonged, mellow effect.
Herbal teas generally have no caffeine in them.
