How Much Does a Gallon of Water Weigh?

How Much Does a Gallon of Water Weigh?

1 US Gallon = 8.34 lbs or 3.785 kg

What is a Gallon?

A gallon is a unit of volume measurement in the US customary and imperial systems, abbreviated as “gal”.

  • The gallon has one characterization in the imperial system and two definitions (liquid and dry) in the United States customary system. Historically, there were many definitions and reconsiderations.

English system gallons

A liquid measurement in the United Kingdom before the 19th century.

Imperial gallon

There are four quarts in a gallon, the imperial pint is defined as 0.56826125 liters (i.e. 1/8 gallon) and there are 20 imperials fluid ounces in an imperial pint.

US liquid gallon

The US gallon is legally defined as exactly 3.785411784 liters.

US Dry gallon

The US dry gallon is not used in commerce, it’s equal to exactly 268.8025 cubic inches.

(Info. Courtesy: Wikipedia)

US gallons (Liquid) vs.UK gallons Calculations

UK gal = US lqd gal = 0.83267

Now let us start the topic and here it is…

We could very easily resolve the answer to this question by getting some basic concepts and methods of the “inter-web” or “internet” or offline somewhere in libraries or math books at home.

To determinate and find something in our way and keep searching from the other sources, is not only educational, but it is self-empowering!

Let’s get it briefly…

Nowadays everything on this earth can easily be uncovered by using different units of measurements made by men. Like Solid and Gas or anything, even liquid can be determined by different available measurements or a well-known unit called gallon.

A gallon measures a unit capacity of liquid in both the US customary units and the British imperial system for long.

Mainly three different types of gallons are being used today, namely the imperial gallon used in Canada, UK and some Caribbean countries, the US gallon utilized mainly in the US and some Latin American countries, and the US dry gallon is in rare use or not being used in commerce. The three sizes of measurements are significantly different as we already have discussed it.

So, now we will go ahead…

Question: How much does a gallon of water weigh?

How Much Does a Gallon of Water Weigh?

Do you know the answer?

1 US Gallon = 8.34 lbs or 3.785 kg

1 Imperial Gallon (UK) = 10.022 lbs or 4.546 kg

But the water temperature effects on Weight.

So, We have Ballpark Calculation for more accuracy (for all temperatures)

  • 1 gallon = 3.75 liters
  • 1 liters = 1 kilogram (density of water is 1 kg/li)
  • 1 kg = 2.2 lbs


3.75 kg = 8.25 lbs

1 gallon = 8.25 lbs

Water Temperature Effects

The weight is variable depending on density, which is affected by the temperature of water and altitude of the location.

Cold liquid or water is denser than a warm one. So, a curious dimension of the core, due to hydrogen bonding. One gallon of warm water would weigh little lesser than a gallon of chilled water. The exact conflict would count on the temperatures in question, yet mostly it doesn’t affect the value.

Read This: How many tablespoons in a Cup?

However, the earth’s main force gravity affects weight too, so one gallon of water or any liquid would weigh more on another planet which is larger than earth like Jupiter, and less on the lesser gravity force like Moon.

Still, we have an old school calculation to remember easily


  • 1 gallon = 128 fl oz
  • 1 pound = 16 fl oz
  • 16 oz = 1 lb
  • 1 oz = (1/16) lb
  • 128 oz = (1/16) X 128 = 8 lbs

So, a gallon weighs approximately 8 lbs.

So, let’s have some practical quiz to sharp our brain 😎

How much do 40 gallons of water weigh in lbs?

How much do 40 gallons of water weigh in lbs?

Here, we have two answers. Before we start, we have to decide, whether the US or British gallon is adopted. But first, we need the conversion from lb to liters for the exact measurements.

Read This: How many ounces in a liter?

1 lb of water is equal to 0.4536 liters, no matter the small deviation in the density from unity at atmospheric temperatures.

US 1 gallon = 3.785 litres

Hence, 40 US gallon weigh

40 x 3.785/0.4536 lb (not lbs), or 333.8 lb

  • British Imperial 1 gallon = 4.546 liters

So, 40 Imperial gallons weigh

40 x 4.546/0.4536 (not lbs), or 400.9 lb

Let make it a little tricky to solve

How much does one gallon of freshwater weigh, after the maximum amount of salt that is soluble at room temperature is added?

How Much Does a Gallon of Water Weigh?

First, we have to know that, what is the maximum amount of salt we can dissolve in one liter of water?

Let’s say a US liquid gallon is equal to 3.785 liters (abt 8.25 pounds) and we reckon freshwater with density 1.000, and we can dissolve about 1.514 Kg of salt, after that the weight of the said gallon of water will be about 5.3 Kg after adding salt (about 11.7 lbs).

  • US 1 gallon = 3.785 litres or 8.25 lbs

Hence, after dissolving maximum salt in water

US 1 gallon = 8.25 lbs + 3.45 lbs (salt weight) =11.7lbs

Note: after adding salt, water volume also will change slightly, but not with the volume combined of the two substances, water, and salt, it will be about 3.94 liters.

Read This: How many ounces in a gallon?


1 US Gallon = 8.34 lbs or 3.785 kg

1 Imperial Gallon (UK) = 10.022 lbs or 4.546 kg

1 US Dry gallon of water is defined as 9.71 lbs

The weight of water was formed as 1 kg/liter.

Atmospheric force and gravity pull also affect the weight of a gallon of water or any other liquid substance.

Higher gravitational pull means more weight and a lesser gravity force has less weight. Example, The weight differences between different planets like The Earth, The Moon or The Jupiter.

I hope you got your answer for the “How Much Does a Gallon of Water Weigh?”

However, like the temperature of the surroundings, the value of water or any of the liquid does not change with a change in gravitational pull.

So, in the end, I would like to say keep drinking fresh water and don’t increase your weight 😀 (kidding). I mean drink plenty of water and stay fit and sharp.

Thank you for your visit, Much Love 💓

How Much Does a Gallon of Water Weigh?

Leave a Comment