Weight of a Gallon of Water
A gallon of fresh water weighs 8.34 pounds. If you want to verify this you can simply fill up a gallon jug and place it on your bathroom scale.
There is an old cooking phrase which addresses the weight of water and other similar liquids (and in some cases, solids) used in the preparation of foods: "A pint's a pound the whole world 'round". Actually, a pint of water weighs 1.04375 pounds. So, although this phrase does not provide the EXACT weight of each liquid, it does provide a very simple rule for determining approximately how much liquids weigh. In the case of water, there are eight (8) pints of water in a gallon. Using this rule, a gallon (eight pints) would weigh approximately eight (8) pounds, which is very, very close to a gallon of water's exact weight of 8.35 pounds which is found in the more detailed and scientifically correct answers to this question. Although pints of milk, gravies and sauces are denser and actually weigh more than a pint of water, the cook can generally use his/her own judgment as to how much other liquids actually weigh. If you have an accurate weight scale, you can quite easily verify these figures.
So, if you're not building a rocket ship, making chemical compounds or medicines or any other things which would require EXACT measurements, remember the simply ditty: "A pint's a pound the whole world 'round."
Here are more answers from other FAQ Farmers:
One liter of water weighs 1 kg., and 1 gallon of water is equal to 3.7854118 liters; therefore, 1 gallon weighs 3.7854118 kg, which is 8.345404487293294 pounds. But at what temperature? Temperature matters a bit.
1 gallon of fresh water is about 8.36
According to the 21st edition of The Machinery's Handbook, 1 gallon of water weighs 8.337 pounds.
To answer this question more appropriately you would have to know the temperature of the water. As water cools it becomes denser until it reaches 39.2 degrees Fahrenheit. Below this temperature the density decreases and the water molecules spread apart. 1 liter of water/ice at this temperature will actually weigh less than 1 liter of water at say 80 degrees Fahrenheit.
One cubic foot of water contains 7.48 gallons of water, weighing in at 62.31 pounds.
The Handbook of Chemistry and Physics specifies the weight of 1 US gallon of water in air at 68 degrees F to be 8.32487 pounds or 3776.103 grams.
To say the temperature of the water affects the weight is somewhat misleading. If you take 1 gallon of room temperature water and place it in a sealed container, the weight will not change regardless of the temperature. Weight is the measure of the pull of gravity on the mass of an object. The mass of water will not change based on temperature, therefore the weight will not change. To be more accurate, the temperature of the water will affect the volume. Ice takes up more space than liquid water. Therefore a gallon of ice will contain less mass than a gallon of room temperature water. The difference in volume is what causes the difference in mass and therefore, the difference in weight. However, it's useful enough to know that 1 gallon of water weighs about 8 1/3lbs.
It is not misleading at all. A gallon is not a measure of mass but a measure of volume and water at different temperatures has different volume to mass ratios. A ounce of ice and an ounce of room temp water are different sizes even though they have the same weight. Likewise a gallon of ice and a gallon of room temp water have different weights even though they are the same size.
One gallon of water, at 20 degrees Celsius, weighs 8.33 pounds.
Gallon: Pounds 8.345404 Grams 3785.4118 Kilograms 3.7854118
Some simple calculations: 2 Pints to the quart. 4 quarts to the gallon. Knowing the above, remember the following little verse: "A pint's a pound, the world around." Two pints per quart, make a quart weigh 2 pounds. Four quarts per gallon make the gallon weigh 8+ pounds.
I'm assuming that the naturally occurring amounts of deuterium and tritium are allowed.
All the above refer to a US gallon which is 8 US pints each US pint being 16 fluid ounces. An Imperial (British) gallon is 8 Imperial pints, each Imperial pint weigh 20 fluid ounces. An Imperial pint weighs 1 pound 3 3/4 ounces so an Imperial gallon weighs 9 pounds 12 ounces. So, by using semantics, a pint, we have found, is not a pound the whole world round.
A U.S. gallon (determined by fluid volume at 72 deg. F, at sea level) of fresh water weighs exactly 8.3452641 lbs.
You must first define the system of weight you will you. This would traditionally be the avoirdupois weight system for coarse measurement used in the English System of weights and measures. That system defines one pound as being equal to 16 ounces. The weight standard is set by comparing your sample with 27.7015 cubic inches of distilled water (preferably electrolytically produced to obtain pure water molecules) measured at 62 degrees Fahrenheit at a barometric pressure of 29.92 inches of mercury. The measure must be taken on scales, with the water suspended in the air and measured with brass weights. Then you would define the substance for testing. In this case water. It should be as close to pure as possible. That is, two hydrogen molecules and one oxygen molecule with nothing else in the solution. Dissolved solids and gases would alter the weight. Additionally, the environment must be stable, so suspended gases, solids and foreign liquids need to be absent. Aeration from agitation and contact with molecules of its container kept to a minimum with the surrounding gas being insoluble in the solution being weighed. Using that weight system, the standard gallon is 231 cubic inches of undisturbed water at its maximum density, chilled to 3.98 degrees centigrade. Under these conditions, one U.S. Gallon fluid measurement is equal to 8.3389 avoirdupois pounds.
Conversions 1 ft**3 of water = 7.48 gallons 1 ft**3 of water weight = 62.38 lb. 1 in**3 of water = .00433 gallons 1 in**3 of water weight = .0361 lb. 1 gallon of water = 231 in.3 1 gallon of water weight = 8.34 lb It looks like one gallon of water weighs 8.34 Lbs.
One gallon of water, at 20 degrees Celsius, weighs 8.33 pounds. A general rule of thumb used by cooks is "A pint's a pound the world around." There are 8 pints in a gallon and a gallon weighs about 8 lbs. A pint is not exactly a pound but unless you are dealing with a lot of water it won't make much difference. As stated above a gallon (8 pints) weights 8 1/3 lbs. 3 gallons (24 pints) will weigh 25 pounds, 1 pound more than you would expect. But, this is a little under 4% more than you expect which is not a huge variation.
Do the math. The density of water is 1000 kilos per meter cubed. One cubic meter is 1000 liters. There's 3.79 liters in a gallon. We divide 3.79 by 1000 and that would be how many cubic meters we have. Make a proportion. 1000/cubic meter =x/.0079 cubic meters. 1000*.00379=3.79 kilos which will be about 9 pounds! Yay!
This is a loaded question for sure. Since a gallon of water is a "Volume" and a "Fluid" the answer is: Depends. Depends on the temperature (since, as a fluid cools it contracts and as it warms it expands - at least most liquids anyways). So a Gallon of "PURE" common water weighs (at 68 degrees F) 8.32487 pounds. This includes the small amount of "Heavy Water" it will contain naturally. The water has to be "Pure" since if it is contaminated it will have a different weight depending on the makeup of the contaminates and how much contaminate there is. But, as you can see, as you heat water above 68 degrees F or cool it below 68 degrees F the "Volume" of water will change. Heated water will have less water in the gallon container thus it will "Weigh" less while cooled water will have more water thus will weigh more (that is until water freezes (that's another story all together LOL).
If you consider small changes with temperature, then what about location? If you took a gallon up a mountain or into space it would be minutely further from the center of the earth and weigh minutely less. If it was taken into deep space it would weight next to nothing (although it's mass would stay the same). On Jupiter it would weigh about 19.5 pounds. Also density, if you took water up a mountain then measured a gallon volume it would weight less because it had expanded.