How much caffeine is there in green tea? how does that compare to coffee?

Usually about 25 mg: The amount of caffeine is green tea varies by brand to brand ; also depends how long you steep it, but averages 20-30 mg/cup (with a rage of 11-48)- see http://www.Caffeineinformer.Com/caffeine-content/green-tea the amount in coffee is even more variable, based on brand, how brewed, how much you drink but is generally in the 100-200 mg range.