Weight of a Gallon of Water

Date: 07/29/99 at 23:33:58
From: Shannon Harris
Subject: Weight of one gallon of water

I was trying to figure out how much a gallon of water weighed. I think 
it is 8 pounds, but would like confirmation if possible. Thank you in 
advance for your answer.

Shannon

Date: 07/30/99 at 12:52:22
From: Doctor Rick
Subject: Re: Weight of one gallon of water

Hi, Shannon.

A gallon of water weighs 8.34 pounds. Your estimate is what many 
people remember as a rule of thumb.

- Doctor Rick, The Math Forum
  http://mathforum.org/dr.math/   

Date: 07/30/99 at 13:10:14
From: Doctor Fwg
Subject: Re: Weight of one gallon of water

Dear Shannon,

One gallon (in volume) is equivalent to 3,785 cubic centimeters (i.e. 
3,785 cm^3). If the density of water is assumed to be exactly 1.0 
g/cm^3, then the mass of one gallon of water would be 3,785 g (from 
3,785 cm^3 x 1.0 g/cm^3 = 3,785 g). And 3,785 g of water is equivalent 
to 8.346 lb. near the earth's surface because a 1,000 g mass near the 
earth's surface would weigh about 2.205 lb. However, the density of 
water varies somewhat with temperature and pressure, so the exact 
weight of a gallon of water might vary a little from the number I have 
given here because I have assumed that the water density is exactly 
1.0 g/cm^3 and this is an approximation.

I hope this answers your question.

With best wishes,

- Doctor Fwg, The Math Forum
http://mathforum.org/dr.math/