Free · Unit conversions

Gallons to Mass Using Liquid Density

Convert US liquid, imperial or US dry gallons to mass using a positive density, with exact gallon definitions and reversible mass units.

  • Formula & worked example
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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

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Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

One US liquid gallon at 1,000 kg/m³ has a mass of exactly 3.785411784 kg under that density assumption. One imperial gallon at the same density has a mass of 4.54609 kg.

Mass = density × volume; one US liquid gallon = 0.003785411784 m³

Worked example

Enter these known values and leave the other values blank.

Density
1000 kg/m³
Volume in the selected gallon type
1 US gal
Mass in kilograms
3.79 kg
Same mass in another unit
0.0037854 t

Assumptions and limitations

  • Volume does not determine mass by itself: supply the substance density at the relevant temperature and pressure.
  • The default density approximates water. It is an assumption, not a universal water density; the retained imperial preset is rounded to 62.43 lb/ft³.
  • US liquid, imperial and US dry gallons are different volume units. Check the selector; the default is the US liquid gallon.
  • The model computes mass, not gravitational force. The selected mass units express the same amount without adding container weight.
  • Zero volume or mass is accepted. Density must be positive, and negative physical amounts are rejected.

Common questions

Why is one gallon not always the same number of kilograms?

Different substances have different densities, and US and imperial gallons also have different volumes. Both the gallon definition and density must be specified.

References

Bookify rejects negative volume and mass while retaining zero amounts and positive density. The US dry gallon uses one eighth of a 2150.42-cubic-inch bushel, replacing the rounded captured volume factor. Bookify replaces the captured rounded US gallon with the exact 3.785411784-liter definition. Bookify uses exact customary mass and volume definitions for density units, replacing rounded factors in the reference. Prices per thousand US gallons use the same exact gallon as the volume inputs.

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