Whenever I took a gallon water bottle from some store, the first thing that struck me was how much is it weighing? So I decided to do some research to find out the exact weight.

So the weight of a gallon of water? A US gallon of water weighs about 8.35 lb or 3.80 kg at average pressure and temperature. An imperial gallon weighs 10.02 lb or 4.54 kg at 4C/ 39F. However, the weight of a gallon varies with density of water which in turn depends on the temperature and pressure that it is stored in.

So a gallon is volume measurement which will change according to the outdoor or storage conditions. Weight per gallon fluctuates. Most of the time the average weight of a gallon is accounted for.

US UNITS  Pound  OunceKilogram
Gallon (4 quarts)      8.35 lb133.6 oz3.787 kg
Quart   (2 pints)    2.087 lb33.4 oz0.9467 kg
    Pint (2 cups)  1.043 lb16.7 oz0.4733 kg
    cup  0.5218 lb8.35 oz0.2367 kg

One cubic feet of water contains precisely 7.48052 gallons.

The Different types of Gallon

Gallons are a unit of measurement of volume but it’s not the same for every country. Gallon measurements vary in different countries depending on the system they follow. Two main schools of thought that are followed are the US system and the British imperial system.

So there exists US gallon, British imperial gallon and US dry gallon.

  • US gallon is equivalent to 3.785 liters or 231 cubic inches.
  • Imperial gallon is equivalent to 4.546 liters or 277.4 cubic inches.
  • US dry gallon is equivalent to 4.405 liters or 268.8 cubic inches.

US dry gallon is a very rarely used term for measurement of different granular agricultural commodities like grains, grapes and apples.

Imperial gallon is used in commonwealth countries which include India, Pakistan, Australia, Canada, UK and numerous other countries.

As the volume of both gallons is different so obviously the weight also differs. Imperial gallon weighs significantly higher due to its greater volume capacity.

  • A US gallon weighs at 8.34 lbs or 3.78 kg at 62 degree Fahrenheit or 17 degree Centigrade.
  • An imperial gallon weighs at 10.02 lb or 4.54 kg at 39 degree Fahrenheit or 4 degree Centigrade.

Effects of Water Temperature on Weight

Temperature is a key factor to dictate the weight of water in a specified volume. We all know that temperature is actually the measure of energy that water molecules possess.

Thus when temperature increases the molecules start vibrating with higher energy, pushing their neighbor on side. This results in lesser molecules in a specific volume; which is in turn density of that solution.

Keeping this in view we know

  • Warm water will have lesser molecules in specific volume
  • Cold water will have more molecules in specific volume

Gallon is nothing but a specific volume. So a gallon filled with warm water, thus containing lesser molecules of water, will weigh less. In contrast, a gallon filled with cold water will weigh more. For example, a gallon of water weighs about 8.34 at 17 degree centigrade while at 1000 degree centigrade it weighs around 8.05.

Hence, a gallon will weigh more when it is filled with colder fluid.

Atmospheric Pressure and Gravity

Pressure and gravity are also the factors that play a vital role while calculating the exact weight of a gallon of water or any other object as well.

If you are on the moon with a gallon of water, it will feel much lighter than you being on Earth. Similarly on a larger planet like Jupiter where gravitational pull is stronger, a gallon of water will be much heavier.

This shift in gravity can also be observed on the earth surface but to a very limited extent.

  • On a place which is closer to the earth core gravity of earth acts stronger.
  • On mountains which are obviously away from the core, gravity is weaker.

Gallon of water will weigh more on areas closer to the core of earth than on hilly areas.

Weight of gallon of different types of water

Water can be in different shapes and forms. In nature, it is available in ponds, rivers, canals and seas. Tap water or fresh water weighs differently from sea water. So for the sake of comparison here’s the weight for a Gallon of different types of waters.

All readings are present at standard temperature and pressure for US gallon.

  • A gallon of distilled/fresh water weighs 8.35 lb.
  • A gallon of sea/ ocean water weighs 8.556 lb.
  • A gallon of saturated sugar water weighs about 8.42 lb.
  • A gallon of ice or frozen water weighs about 7.71 lb.

Gallon Conversion to other units:

In order to convert Gallon into liters, the following are the formulae for both US and Imperial gallon.

For US standard

 Volume in Liters = (volume in gal) x (3.785 L/gal)

For imperial gallon

Volume in Liters = (volume in gal) x (4.5460 L/gal)

Now we can easily convert this into weight as for water 1 liter ≈ 1 kg ≈ 2.2 lbs.

Hence, UK or Canadian gallon of water weighs…..

4.546 × 2.2 = 10.0012 pounds

4.546 × 1 =  4.546 kg

US gallon of water weighs

3.785 × 2.2 = 8.327 pounds

3.785 × 1 = 3.785 kg

5 UK gallons of water weigh

5 × 10.0012 = 50.006 pounds

5 × 4.546 = 22.73 pounds

5 US gallons of water weigh

5 × 8.327 = 41.635 pounds

5 × 3.785 = 18.925 kg

How Much Does a 5 Gallon Jug Of Water Weigh?

Drinking water usually comes in the form of jugs or 5 gallon water bottles. In the US 5 gallons jug weighs 41.64 lb or 18.89 kg. While in the UK, 5 gallons jug weighs 50 lb or 22.67 kg.

                       Weight in pounds and kgs of gallons of water

Gallons of

       US standard system

          UK imperial gallon





1 gallon





2 gallons





3 gallons





4 gallons





5 gallons





6 gallons





7 gallons





8 gallons





9 gallons





10 gallons





Gallon of Water, Milk, petrol and Diesel weight compared

So as we know a gallon of fresh water weighs 8.35 lb. Let’s compare it with a gallon of different commonly available fluids

  • A gallon of milk weighs 8.6 lb or 3.9 kg
  • A gallon of gasoline weighs 6.3 lb or 2.86 kg
  • A gallon of diesel weighs about 7 lb or 3.175 kg

So a gallon of water is lighter than a gallon of milk. While a gallon of water is much heavier than a gallon of both gasoline and diesel.

So it tells us the density of gasoline and diesel is lesser than water; while that of milk is higher.

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