How much does a gallon of water weigh?

Just the way we measure the weight of solid objects with the unit of measurement referred to as Kilograms or Pounds, the weight of the water is measured in terms of Gallon. But wait, isn’t Gallon a measure of volume, right?

Well, you are right. The water is measured in terms of Gallon, and the unit measures the volume of water (or for that matter any other fluid). But, how much does a gallon of water weigh? While we can provide you with a straight answer, we thought we would give serious thought and find out how to arrive at the calculation.

A Gallon of Water – Three Different gallons

Are you confused yet again? Well, that would mean we have three different types of gallons. And that is precisely why it would be extremely difficult to answer the question – how much does a gallon of water weigh?

The answer to that question varies considerably. People give different answers to the question, and the answer varies from  5 to 15 pounds. During the initial days, the weight of the water was defined as 1 litre of water weighs one Kg. However, as the studies later showed that the density of the water is influenced by the temperature and atmospheric pressure. Thus this theory was discarded.

The weight of one Gallon of water is dependent on the Gallon measurement that you are using. The US measurement of Gallon makes use of two different units. The UK Gallon, on the other hand, uses yet another unit.

There are two Gallon measurements used in the US. One of them is Dry Gallon which is equivalent to 268.8025 cubic inches or 4.405 liters. The Liquid US gallon is equivalent to 231 cubic inches, which is equal to 3.785 liters.

The UK Gallon, the third-gallon measurement, is equal to 10 Pounds of water. Do note that all these measurements are based on the maximum density of the water.

How much is then a Gallon of Water?

Like we stated already, the Gallon of water is dependent on which unit of Gallon you have been using. The following calculations should sum it up based on the Gallon you pick –

  • One US Dry Gallon of water = 4.405 Litres
  • One Liquid US Gallon of water = 3.785 Litres
  • One UK gallon = 4.546 Litres

Do note that when we discuss a Gallon of water, we ideally refer to the US measurement of Gallon.

What factors affect the weight of water?

Well, the weight of the water can be affected by a wide range of factors. The major two factors that would affect the weight of the water are the temperature of the water and the atmospheric pressure prevalent at the location where you are measuring the weight of water.

Gravity is yet another factor that can affect the weight of water per Gallon.

Effect of temperature on the weight of water

Cold water will have more density and thus will weigh more in less volume. The density of warm water, or the water that is just freezing or even the water that is in the form of ice would be more less than that of the cold water.

This inequality or uniqueness is caused by a concept referred to as Hydrogen Bonding. The weight of one Gallon of cold water will thus be more than a  gallon of warm water. The exact difference would be dependent on the actual temperature, and therefore you would find it a little difficult to arrive at. However, studies say that there is not much difference.

The key idea to remember here is that hotter water weighs less, and colder water weighs more.

Effect of Atmospheric Pressure and Gravity on the weight of water

Atmospheric pressure and gravity are the other two features that would affect the weight of one Gallon of water considerably. As an example, a gallon of water on the moon would weigh less than that on the earth. More gravity would translate into more weight.

So, how much does a gallon of water weigh?

Well, we come back to the same question once again. How much does one gallon of water weigh? The water does attain the maximum density at 4 degrees C. At this temperature, a gallon of water will weigh 8.345 pounds. At a temperature of 200 degrees F, the weight a gallon of water will reach just 8.04 pounds.

If you are checking out the weight of a gallon of water at room temperature which we all have been looking ahead to, it would be around 8.33 pounds or 3.78 Kgs.

So, we have the answer – although approximately – a gallon of water will weigh 8.33 pounds.

An easy way to remember the weight of a gallon of water

Well, if you are preparing for an examination and find it rather difficult to remember how much does a gallon of water weigh, there is one simple formula that can help you find out and remember it.

Just remember one simple rhyme for the purpose – A pint’s a pound, the world round. That is precisely how you would be able to remember how much does a gallon of water weigh. The saying is based on the relation between 16 fluid ounces (a pint) and 16 ounces avoirdupois weight. A pint is equivalent to a pound. A gallon is equal to 4 quarts which translates into 8 pints, and thus it would mean a gallon of water is equal to approximately 8 pounds.

The Concluding Thoughts

Well, that should have helped you to understand the concept of the weight of a gallon of water weight. The above discussion should ideally help you arrive at the best options to find an appropriate answer to your question on how much does a gallon of water weigh.

We assume the tips outlined here should ideally help you arrive at the best options to understand and find an answer to get access to the right answers for the weight of one Gallon of water.