How much does 1 gallon of 90 proof liquor weigh?

One gallon of 90 proof liquor weighs approximately 7.5 to 8.0 pounds. The weight can vary slightly based on the specific alcohol content and the ingredients used in the liquor. Since 90 proof means the liquor is 45% alcohol by volume, it is denser than water, which weighs about 8.34 pounds per gallon.