How much does a gallon of water weigh?

Question

How much does a gallon of water weigh?

Answer 1

8 lbs.

Answer 2

70

Answer 3

I just needed to support Joseph's answer. He's got the right answer. easiest answer is 8.34lbs, but I don't really know about imperial gallons. Just that US gallons are different from "other gallons" (which is why UK people talk about fish tanks in Liters rather than Gallons...  I think)

And to those of you who don't know that a "gallon" is not a weight, but rather a measurement of volume... PLEASE pay more attention in school.

Quick recap:

Volume is the total cubic area that a thing occupies. So, you can have 3 cubic feet of hydrogen. A Gallon is simply another method of measuring volume.

Mass is the amount that an object weighs. So, if you have a pound of lead and a pound of feathers, they both weigh the same, but the pound of feathers will take up a significantly larger volume of space.

If you take the Mass and divide it by it's Volume, you get the object's Density. So, if you have an object that weighs 3 pounds and takes up 3 cubic feet, you get an object that is one pound per cubic foot in density. So, the feathers would be more like 1 pound per 2 cubic feet, while the lead would be more like 1 pound per 1/12 cubic foot.

Do you now understand that when the asker was asking about the weight of one gallon of water, that you telling him that it "weighs a gallon", you are being an idiot?

Please don't answer questions if you have no idea what the answer is. Thank you.

Jeff: But it's ok to answer that a gallon weighs a gallon?

Answer 4

Well judging that it is a GALLON of water I am guessing it ways about... a gallon... or maybe four quarts, or about 128 ounces.  Something around that.  

Answer 5

A US gallon of fresh water at 4 degrees C weighs 8.34 pounds. An imperial gallon at 62deg F (old UK system) weighs 10 pounds.

Answer 6

Alyssa:  Do you realize that a gallon of water does not magically go from 8.3 pounds to 10 pounds when you heat it up to room temperature?  It actually goes down from 8.33 pounds to 8.31 pounds.  Hmmm.   Maybe the discrepancy between 8.3 and 10 pounds has more to do with imperial gallons versus just plain ol' gallons?  

Maybe before trashing someone on answering a question wrong, you should make sure your answer is correct.  

Edit: Alyssa, no, "a gallon weighs a gallon" is a nonsense answer too.  But honestly, the system is totally screwed up so it's not surprising that people are confused.  I mean wouldn't you think a fluid ounce (unit of volume) of water would weigh an ounce?  So you'd think that 16 fluid ounces of water would weigh a pound (a pint), and a gallon has 8 pints, so you'd think that a gallon of water would weigh 8 pounds.  But it doesn't.  it weighs 8.3 pounds.  I think ounces are now defined by grams, not fluid ounces... Screwed up ancient system of measurements just confuses people who are already confused about physics.

Answer 7

there are 3.78541178 L in a US gallon.. and the density of water is 1 g/mL...the formula of mass in relation with density of volume is m=dV..

using this facts:

3.78541178 L--> mL=3785.41178mL

m=(1g/mL)(3785.41178mL)

m=3785.41178grams! or 8.33 lbs