Beer is 95% water. A standard 12 oz beer with 5% ABV contains 11.4 ounces of water with the remaining 5% being alcohol.
When brewing beer at home, you will start with significantly more water than you intend to have beer because of the amount of time the wort will need to boil in order to concentrate the flavors and create the desired complexity.
The standard 12 oz beer is made up of 95% water. That means that, in 12 oz of beer, there’s about 11.4 oz of water. That leaves about 0.6 oz for the stuff that makes you feel funny – alcohol.
Whether you’re drinking a pint of beer (a full 16 oz pour), the same principle and mathematics apply. No matter the size of the pour, you’ll always be looking at about 90-95% water. In this case, a pint of beer contains 15.2 oz (449.52mL) of water.
Beer does contribute to water intake. It also technically hydrates you – for the time being. However, alcohol is a diuretic, and contributes to more frequent urination and thus leads to dehydration.
It can take about 7 gallons of water to make just 1 pint of beer. In other cases, it can take even more – upwards of 10 gallons of water per pint.