The other way to calculate it is how much alcohol is in any given beer. A 12 oz can of Coors @ 5% will have 0.6 ounces of alcohol. (12 x .05) The 20 oz can of 12% beer will have 2.4 oz of alcohol. (20 x .12) So yes, exactly the same as 4 cans of Coors.
There is some other factors such as how long it would take to drink, and your body to then absorb the alcohol.
However if I ever find myself drinking a 20 oz can of 12% beer by myself I don't need to worry if I'm too drunk to drive- as that means I'm at home alone.
