In taking a quick WebMD quiz about caffeine ( Quiz: Myths and Facts About Caffeine ), I read in the 2nd question that 200 mg to 300 mg of Caffeine is considered safe for most adults.
Green Tea has health benefits and a little caffeine (about 26 mg for 180 ml aka 6 fl 0z) . Compare that caffeine to a cup of coffee (about 145 mg of caffeine).
So, green tea is on my radar and I will switch to it soon.
My current favorite drink has about 108 mg per 24 oz. So, I can have about 2 1/2 bottles of that safely.
If I switch to green tea, I can drink how many cups? It's about the same. 24 oz of brewed green tea is about 104 mg of caffeine. :)
If I want to push the limits of safe, I can have 400mg of caffeine according to an ABC News webpage.
Raise your glass and let's drink to good health and productivity!