How to Calculate Pints, Quarts, Gallons to and from Pounds.

Alternate titles might be Volume to Weight Conversions or Weight to Volume Conversions - 8:4:1:8.

Or the relevant questions might be How many pounds in X pints, quarts, or gallons? Or How much does X gallons, quarts, or pints weigh?

A table of most-searched-for questions and answers is also included.

Volume to Weight Conversions. Weight to Volume Conversions. Simple math to convert or calculate pints, quarts, gallons, and pounds.
Volume to Weight Conversions. Weight to Volume Conversions. Simple math to convert or calculate pints, quarts, gallons, and pounds.

First, the quick answers to volume amounts and ratios.

  • 2 pints equals 1 quart.
  • 4 quarts equals 1 gallon.
  • 8 pints equals 1 gallon.

Or, to put it another way...

  • 1 quart equals 2 pints.
  • 1 gallon equals 8 pints.
  • 1 gallon equals 4 quarts.

Converting Volume to Weight

Converting volume to weight has everything to do with the density of the liquid. Fortunately, this question usually has to do with:

A. How much does the gasoline in your gas tank weigh?

And/Or

B. How much does a container of water weigh?

The rule of thumb, and the expression to remember, is: "A pint's a pound the world around." The resulting estimates from this rule will serve you well for most everyday purposes.

Basic Examples Being...

A pint weighs a pound.

There are two pints in a quart; so a quart weighs 2 pounds.

There are four quarts in a gallon; so a gallon weighs 8 pounds.

And the eight pints in a gallon, also weighing 8 pounds.

This pretty much answers the question. Here are some other typical examples...

Some household examples:

  • A 1-quart bottle of Gatorade weighs 2 pounds. Note: there are 2 pints in a quart and 4 quarts in a gallon. As a side note: there are 16 fluid ounces in a pint, 32 fluid ounces in a quart; 1 and 2 pounds respectively.
  • A 2-liter bottle of Pepsi would convert to a weight of a little over 4 pounds. Note: A liter is slightly more than a quart.

Some gallon examples:

  • A 1-gallon container would convert to a weight of 8 pounds.
  • A 5-gallon container weighs 40 pounds.
  • A 10-gallon container weighs 80 pounds.
  • A full, 25-gallon SUV gas tank means you are hauling around 200 pounds of fuel.
  • A typical city water tower can hold anywhere from 300,00 to 600,000 gallons of water, which converts to a weight of 2,400,000 to 4,800,000 pounds of water sitting on those "stilts".

More About Fluid Density

Gold (yellow) and silicon (blue) atoms in a liquid gold-silicon eutectic alloy.
Gold (yellow) and silicon (blue) atoms in a liquid gold-silicon eutectic alloy. | Source

A major component of converting fluid volume to a weight measurement is the density of the fluid. For gasoline, water, and most grocery items; the rule of a-pint's-a-pound will serve you just fine. However, to take an extreme example, the liquid metal/element mercury would totally throw the pint's-a-pound rule out the window. As would any molten metal or alloy.

In the interests of "full disclosure", fluid density is also affected by temperature. This is why many people fill their gas tank first thing in the morning. There is more gas per gallon at 50 degrees Fahrenheit than at 90 degrees Fahrenheit. It should be noted the percentage difference is in the very low, single-digits.

Frequent Q&A

Table of the Most-Searched-For Questions and Answers.

How many pounds...

  • How much does 1.5 quarts weigh? Answer is 3 pounds.
  • How much does 2 quarts weigh? Answer is 4 pounds.
  • How much does 3 quarts weigh? Answer is 6 pounds.
  • How much does 5 quarts weigh? Answer is 10 pounds.
  • How much does 6 quarts weigh? Answer is 12 pounds.
  • How much does 10 quarts weigh? Answer is 20 pounds.
  • How much does 16 quarts weigh? Answer is 32 pounds.


  • How much does 5 gallons weigh? Answer is 40 pounds.
  • How much does 10 gallons weigh? Answer is 80 pounds.
  • How much does 15 gallons weigh? Answer is120 pounds.
  • How much does 20 gallons weigh? Answer is 160 pounds.
  • How much does 50 gallons weigh? Answer is 400 pounds.
  • How much does 55 gallons weigh? Answer is 440 pounds.


  • How many pints in a pound? Answer is 1.0 pints.
  • How many quarts in a pound? Answer is 0.5 quarts.
  • How many gallons in a pound? Answer is 0.125 gallons.

Some Volume Formulas

The formulas for the volume of a sphere, the volume of a cube, the volume of a cylinder, the volume of a rectangular prism.
The formulas for the volume of a sphere, the volume of a cube, the volume of a cylinder, the volume of a rectangular prism. | Source

Some More Water and Gasoline Volume-to-Weight Examples

Depending on what unit of measurement you use, volume will equal cubic English or cubic Metric; examples being cubic inches or cubic centimeters.

English

  • 29 cubic inches equals ~1 pint, which equals ~1 pound.
  • 58 cubic inches equals ~2 pints, which equals ~1 quart, which equals ~1/4 of a gallon, which equals ~2 pounds.
  • 231 cubic inches equals ~4 quarts, which equals 1 gallon, which equals 8 pounds.

Metric

Most of the world uses Metric. There is a reason for that. As an example, 1000 cubic centimeters equals one liter, 1000 grams equals one kilogram, etc.; all nice, neat, and tidy... The United States and others are trying to get with the program; Metric is already included with English measurement on most U.S. consumer items. It's only a matter of time.

Note: the tilde (~) is the mathematical symbol for approximate.

Water Tank Size and Volume Formula

And how much does the water weigh in a full water heater.

How much does the total amount of water in a water heater weigh? Volume to Weight Conversion.
How much does the total amount of water in a water heater weigh? Volume to Weight Conversion. | Source

From the above NASA chart we see the volume formula for a cylinder is V = (πd2h)/4.

Water tank heaters come in all sizes. For the purposes of this example, we will say the water tank heater has a measured height of approximately 54 inches; what with this, that, and the other, the water part is probably around 48". The diameter measured as 18"; what with insulation, etc., 16 probably works.

So...

d = 16

h = 48

Thus,

V = (3.14 * 16 * 16 * 48) divided by 4.

Since all numbers are inches, the answer will be in cubic inches.

V = (3.14 * 256 * 48) divided by 4.

V = (3.14 * 12288)/4

V = 38514/4

V = 9646 cubic inches

231 cubic inches is equal to a gallon, so we divide 9646 by 231.

9646/231 = 41.76 gallons.

What with the inner measurements being estimates, looks like it is a 40 gallon water heater.

A gallon weighs 8 pounds.

So multiplying 40 times 8 gives 320.

A 40-gallon water heater contains 320 pounds of water.

Knowing the volume and weight of a 40-gallon water tank heater makes it easy to extrapolate the volume and weight of other water heaters.

  • 10 gallon water heater is 2310 cubic inches and the water weighs 80 pounds.
  • 20 gallon water heater is 4620 cubic inches and the water weighs 160 pounds.
  • 30 gallon water heater is 6930 cubic inches and the water weighs 240 pounds.
  • 40 gallon water heater is 9240 cubic inches and the water weighs 320 pounds.
  • 50 gallon water heater is 11550 cubic inches and the water weighs 400 pounds.
  • 80 gallon water heater is 18480 cubic inches and the water weighs 640 pounds.
  • 100 gallon water heater is 23100 cubic inches and the water weighs 800 pounds.

A side note: a cubic foot is 12 inches times 12 inches times 12 inches. So, 1728 cubic inches equals 1 cubic foot.

A second side note: If you are not familiar with algebra, it is a lot easier than most people think. If interested, here is a complete algebra tutorial for beginners. And there is also a separate page about pi.

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Comments 2 comments

leroy64 profile image

leroy64 4 years ago from Dallas, Texas (Oak Cliff)

I like this article, especially the part about temperature and gasoline. I am filling up in the morning from now on. When I am cooking it's easier (faster) to just weigh the liquids - assuming the recipe calls for liquids in weight instead of volume.

FYI - The part about the US converting to metric, everyone has been saying "It's only a matter of time" for most of my 48 years on this earth. Is changing to metric a good idea? Probably. Is it going to happen in my lifetime? I doubt that I will live long enough to see it happen.


Chinaimport profile image

Chinaimport 2 years ago from Guangzhou

A useful hub for those math challenged readers. My country was implementing a shift from Imperial to decimal system so I learned both. This was followed by a forced learning of US measurements when I stayed in Philadelphia for a couple of years, leaving me utterly confused for a lifetime.

A complete shift to decimal system will solve most of the conversion problems.

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