# How Much Does One Gallon Of Water Weigh?

The density of water is 1 and density is mass divided by volume so 64 ounces of water (a gallon) weighs 64 ounces which is 8 pounds.  In fact, water is used as the basic unit for the metric system, just as water's freezing point is 0 degrees Celsius and it's boiling point is 100 degrees celsius, water defines mass and volume in the metric system because it has a density of 1.  There are answers that will say 8.33 or 8.34, but those are under certain conditions.  That is where the saying, "a pint is a pound the world around" came from--a pint of water weighs a pound.
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Vernon Pardue commented
You confused your ounces. Your formula for density uses volume (which would be fluid ounces.) However your explanation switches to weight (which is pounds and ounces.) This mistake is not uncommon, but it further confuses the reader.
A liquid measure of one ounce of water by volumn at 62 degrees fahrenheit, under one atmosphere of pressure (14 pounds per square inch), by definition, weighs one ounce. In Britain (UK), where the imperial standards of weights and measures were established, a gallon has 160 ounces. Therefore an imperial gallon of water is 160 ounces - or exactly 10 pounds. In the United States of America one gallon of water at 62 degress fahrenheit and one atmosphere of pressure has 128 ounces - or exactly 8 pounds. A liquid measured U.S. Gallon by volumn at 39.2 degrees fahrenheit (4 degress celsius) under one atmosphere of pressure weighs 8.34 pounds.
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64 ounces is not 1 gallon.
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The more detailed and scientifically correct answer of this question is as follows;

There are eight (8) pints of water in a gallon and it means a gallon is equal to 8 pounds. This is close to a gallon of water exact weight 8.35 pounds. So 8.35 pounds is the right answer.
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8.345404 lbs. Is the result of converting 3.78541178 l/gallon and multiplying that by 2.20462262 lbs/kilogram
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A US gallon of fresh water that is at 4 degrees Celsius weighs 8.34 pounds. And an imperial gallon at 62 degree F (old UK system) weighs exactly 10 pounds.
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