Beer contains alcohol, and too much alcohol is bad for you. The difficult part is determining where the limit for "too much" is. Beer is also quite high in calories, so even if it wasn't for the alcohol, too much beer could still be bad for you.
Sorry, it isn't measured in how much beer you drank. The measurement is what percentage of your blood is alcohol. The total number is going to vary based on the strength of beer, how much you weight and how fast you drank them.