Complete Solution: How Much Does a Gallon of Water Weigh?

Are you exploring to know about how much does a gallon of water weigh? Covering approximately 70 percent of the world’s surface, water is the most abundant molecule on the face of the Earth. Just above the body in the Earth’s atmosphere, water also abounds in the form of water vapor. It is only the chemical compound that lives naturally in solid, liquid, and gas states.

The chemical formula of water, H2O, is one of the most well-known chemical formulas. The H stands for hydrogen with the subscript 2 for the number of hydrogen atoms, and O for one oxygen atom; all three bits are joined together via covalent bonding, which means that they share electrons.

Another unique water source is that it is less dense when it is frozen solid than in liquid form. This is the reason why ice cubes float in beverages. Water is used as a coolant because it can absorb a fair amount of heat before its temperature rises.

how much does a gallon of water weigh in pounds
how much does a gallon of water weigh in pounds

Three Different Units of Gallon

It makes a difference in which unit of gallon you are using. There are two US definitions of the gallon. The US liquid gallon (most commonly used) is specified as 231 cubic inches, which is 3.785 liters, and weighs 8.344 lbs at its highest density.

The US dry gallon is defined as 1/8th of a US bushel, 268.8025 cubic inches, or 4.405 L. The weight of a US dry gallon is 9.711 lbs of water at its greatest density.

The UK gallon or imperial gallon formerly was defined as 10 lbs of water, but the modern definition is exactly 4.54609 L or 10.02 lbs of water at its maximum density.

How much is a Gallon of Water?

If we’re talking about the weight of a gallon of water, we need to be clear about what a gallon is.

  • In the US, a gallon is 128 fluid ounces or 3.785 liters.
  • In the UK, however, a gallon is 160 fluid ounces or 4.546 liters. (We’ve got more on that insanity.)

For the purpose of the question, ‘How much does a gallon of water weigh?’, we will focus on the American gallon (128 floz).

How Much Does Water Weigh?

People used to go by the rule that a liter of water weighed a kilogram. Simple, huh? The metric system’s beauty is in its tidiness: 1cm³ of water is 1ml and weighs 1g. So 1L of water (1000ml) weighs 1kg (1000g).

What is the Total Weight of a Gallon of Water?

A US gallon of water weighs around 8lb, but the exact measurement depends on a couple of environmental factors that we’ll walk you through now.

What Changes the Weight of Water?

As you’ll know from boiling water on the hob or freezing it into cubes, water can change its state. These are extreme examples, but even moderate fluctuations in Temperature do affect the behavior, and therefore the weight, of water.

Similarly, just as the weight of water would be different on land, at the bottom of the ocean, or on the moon, atmospheric changes impact its mass.

How does Temperature Affect the Weight of Water?

When you heat water, you increase its energy. Water molecules get excited and start bashing each other around like a crowd of rabid shoppers on Black Friday. The amount of space each molecule now needs is more significant because they’re spinning around, high-kicking and elbowing one another, instead of standing calmly in line. So increasing the energy (i.e., heat) of water decreases its density. Molecules become more spaced out.

Therefore, if you have a gallon pitcher that you fill with cold water from the tap, it will weigh more than a boiling water pitcher. The mean water density is more significant, so more molecules fit in a given space (the gallon pitcher) than in hot water.

How Much Does a Gallon of Water Weigh?

Water is most dense when it’s at 39.2ºF or 4ºC. At this Heat, a gallon of water weighs around 8.345lb. Turn the heat way up to 200ºF, though, and a gallon of water will weigh around 8.04lb. At room heat (70°F or 21°C), a gallon of water weighs 8.33lb (3.78kg).

1 Gallon of Water (Room Temperature): 8.33lb

Check out the reference table below to see how gallons of water translate into pounds and kilograms and try out our water weight calculator yourself! If you want to find out the weight of any other liquids, give our gallons to pounds converter a try.

how much does a 5 gallon bucket of water weigh
how much does a 5 gallon bucket of water weigh

Easy Way to Remember the Weight of Water

While you’ll want to keep the exact volume meanings in mind for scientific calculations, for everyday use, you can remember the weight of water using the simple rhyme: A pint’s a pound, the world around.

The saying applies to the rough equivalence between 16 fluid ounces (a pint) and 16 ounces avoirdupois weight. A gallon is 4 quarts or 8 pints, so a gallon weighs about 8 lbs.


Q: How much does 1 gallon of frozen water weigh?
A: This mass weighs 3,4822 kg * 9,81 N/kg = 34 160 Newtons.
Q: How much do 70 gallons of water weigh?
A; I’m afraid my stand is going to give once I get the water in it 🙁 At 70º F, water weighs 8.329 pounds per US gallon. Seventy-two gallons at 8.329 = 599.688 lbs plus the tank itself, 630 lbs.
Q: What is the most massive liquid on Earth?
A: Mercury is the densest liquid at standard requirements for temperature and pressure (STP). Also called quicksilver, mercury has been known for more than 3,500 years. It is an essential metal in industry, but it is also toxic.
Q: What's more massive milk or water?
A: A cubic meter of milk (1000 liters) weigh between 27 and 33 kg more massive than water. That’s because milk is about 87% water and all the other substances, excluding fat, are more massive than water.


I hope you have enjoyed reading about how much does a gallon of water weighs? It was all about gallon units and a complete explanation on how much does a gallon of water weighs? Share your valuable thoughts and suggestions in the comment box section below.

Leave a Comment