kg to Gallons Converter
Converting kilograms to gallons requires the density of the substance, because kilograms measure mass while gallons measure volume. Select a substance, enter a mass or a volume, and the converter gives you the other value instantly, in US or UK gallons. Switch the direction to go from gallons back to kilograms, and use the custom-density option for any liquid not in the list.
Formula
Worked example
To convert 10 kg of whole milk (density 1.030 g/mL) to US gallons: 10 / (1.030 x 3.7854) = 10 / 3.899 = 2.565 US gallons. To reverse: 2.565 US gal x 3.7854 x 1.030 = 10.0 kg.
Why you need density to convert kg to gallons
Kilograms measure mass; gallons measure volume. Mass and volume are only directly comparable when you know the density of the substance. Density tells you how much mass is packed into a unit of volume. For water at room temperature, density is almost exactly 1 kilogram per litre, so 1 litre of water weighs 1 kg. For gasoline, density is roughly 0.745 kg/L, so a litre of petrol is lighter. For honey, at about 1.42 kg/L, a litre is heavier than a litre of water. The formula is: volume in litres = mass in kg divided by density in kg/L. Once you have litres, you multiply by 0.264172 to get US gallons, or by 0.219969 to get UK gallons.
US gallon vs. UK gallon: what is the difference?
The US gallon is defined as exactly 3.785411784 litres. The UK (imperial) gallon is larger, defined as exactly 4.54609 litres. That means a UK gallon holds about 20 percent more liquid than a US gallon. In everyday terms: 1 US gallon of water weighs about 3.785 kg, while 1 UK gallon of water weighs about 4.546 kg. When a recipe, fuel specification, or shipping manifest says "gallons" without specifying, always confirm which gallon is intended, as the difference is significant.
Practical uses for this conversion
The kg-to-gallons conversion appears in several real-world contexts. In fuel logistics, tanker and pipeline volumes are often measured in gallons while customs documents list weight in kilograms; the conversion needs the correct fuel density for the grade and temperature. In food production and brewing, ingredient recipes may be written in either system and accurate conversions help scale batch sizes. In chemical handling and environmental reporting, reagent quantities may be specified in kilograms while storage containers are rated in gallons. In shipping and freight, weight and volume can both determine charges depending on the tariff structure, so knowing the equivalent volume from a given mass is useful for planning.
How temperature affects density and the conversion
Density is not perfectly constant: most liquids expand slightly when heated and contract when cooled. Water, for example, is densest at about 4 degrees Celsius (1.0000 kg/L) and slightly less dense at 20 degrees Celsius (0.9982 kg/L). For everyday purposes the difference is negligible, but in precision engineering, petroleum trading, or laboratory work, temperature-corrected densities should be used. Fuel density tables are typically given at a reference temperature of 15 degrees Celsius. If your application requires high accuracy, obtain the density at the actual operating temperature from a technical data sheet or a certified measurement.
Common substances: density and gallon equivalents
| Substance | Density (g/mL) | kg per US gal | kg per UK gal |
|---|---|---|---|
| Water | 1.000 | 3.785 | 4.546 |
| Seawater | 1.025 | 3.880 | 4.660 |
| Milk (whole) | 1.030 | 3.900 | 4.682 |
| Beer | 1.010 | 3.823 | 4.591 |
| Wine | 0.994 | 3.762 | 4.518 |
| Cooking oil | 0.880 | 3.331 | 4.000 |
| Olive oil | 0.911 | 3.449 | 4.141 |
| Honey | 1.420 | 5.375 | 6.455 |
| Ethanol (pure) | 0.789 | 2.988 | 3.588 |
| Gasoline (petrol) | 0.745 | 2.820 | 3.386 |
| Diesel fuel | 0.832 | 3.150 | 3.781 |
| Crude oil | 0.870 | 3.294 | 3.955 |
| Bleach (household) | 1.084 | 4.103 | 4.927 |
Density values are typical figures at room temperature (~20 C). US gallon = 3.7854 L; UK gallon = 4.5461 L.
Frequently asked questions
How many gallons is 1 kg of water?
Water has a density of approximately 1 kg/L at room temperature, so 1 kg of water equals 1 litre. Multiplying by the gallon conversion factor gives 0.2642 US gallons (about one quarter of a US gallon), or 0.2200 UK gallons. Because water is the standard reference, this ratio is also the simplest way to remember the conversion before density corrections for other liquids.
How many kg is 1 US gallon of water?
1 US gallon equals 3.7854 litres. Since water has a density of 1 kg/L, 1 US gallon of water weighs 3.7854 kg, commonly rounded to 3.785 kg or about 8.34 pounds.
Can I convert kg of milk, fuel, or oil to gallons the same way?
Yes, but you must use the correct density for each substance. Whole milk is about 1.030 kg/L, so it is slightly heavier than water per litre. Cooking oil is about 0.880 kg/L, so it is lighter. Gasoline (petrol) is about 0.745 kg/L. Dividing the mass in kg by the density gives litres, then multiply by 0.2642 for US gallons or 0.2200 for UK gallons. This calculator has built-in densities for the most common substances and a custom field for anything else.
What is the formula to convert kg to US gallons?
The formula is: gallons (US) = mass (kg) / (density (kg/L) x 3.7854). For example, 5 kg of olive oil with a density of 0.911 kg/L: 5 / (0.911 x 3.7854) = 5 / 3.448 = 1.450 US gallons.
How do I convert gallons to kg?
Reverse the formula: mass (kg) = volume (gallons) x 3.7854 x density (kg/L) for US gallons, or x 4.5461 x density for UK gallons. Select "Gallons to Kilograms" in the direction input above and the calculator handles the arithmetic.
Why does the substance matter when converting kg to gallons?
Different liquids have different densities. One kilogram of honey, with a density of about 1.42 kg/L, only fills 0.186 US gallons. One kilogram of gasoline, at about 0.745 kg/L, fills 0.355 US gallons. Using the wrong density will produce a significantly wrong result, so always select the correct substance or enter a measured density.
What is a UK gallon and how is it different from a US gallon?
A UK (imperial) gallon is 4.54609 litres, which is about 20 percent larger than a US gallon (3.78541 litres). This means 1 UK gallon of any liquid weighs about 20 percent more than 1 US gallon of the same liquid. Always confirm which gallon standard is being used when working with international documents or specifications.