Gallons to Kilograms Converter (gal to kg)
Convert between gallons and kilograms for any liquid. Choose your gallon type (US or UK), pick a substance from the built-in list or enter a custom density, then enter either gallons or kilograms and the other value updates instantly. The "Show your work" panel explains every step of the calculation.
Formula
Worked example
1 US gallon of milk: 1 gal × 3.7854 L/gal × 1.032 kg/L = 3.907 kg (about 8.614 lb). For water: 1 gal × 3.7854 × 0.9982 = 3.779 kg.
Why gallons and kilograms are not directly comparable
Gallons measure volume (how much space a liquid occupies), while kilograms measure mass (how much matter it contains). Converting between them requires one more piece of information: the density of the liquid. Density tells you how many kilograms fit into one liter. Water has a density of about 0.998 kg/L at room temperature, so one US gallon of water (3.7854 liters) weighs about 3.782 kg. A denser liquid such as honey (1.42 kg/L) would weigh about 5.38 kg per US gallon, while a lighter one like gasoline (0.737 kg/L) weighs only about 2.79 kg per gallon.
US gallons vs UK (imperial) gallons
The US liquid gallon and the UK imperial gallon are two different units, which is a common source of confusion. One US gallon equals 3.785411784 liters. One UK (imperial) gallon equals 4.54609 liters, making it about 20% larger than the US gallon. If you are converting fuel volumes in the United Kingdom, Canada, or Australia, select the UK gallon option. Recipes and product labels from the United States use the US gallon.
How the converter works: the formula step by step
The calculation has two steps. First, convert gallons to liters: multiply the volume in gallons by the liters-per-gallon factor (3.7854 for US gallons or 4.5461 for UK gallons). Second, convert liters to kilograms: multiply the volume in liters by the density of the substance in kg/L. The result is the mass in kilograms. For the reverse direction (kilograms to gallons), divide the mass by the density to get liters, then divide by the liters-per-gallon factor.
Practical uses: fuel, cooking, and industrial liquids
In cooking and food service, converting gallons of milk, cream, or oil to kilograms is useful when a recipe calls for mass but you measure by the gallon. In the fuel and petroleum industry, selling and taxing fuel by volume (gallons) while calculating load weights in kilograms is standard, and different fuels have meaningfully different densities (gasoline is much lighter than diesel). Industrial processes often specify reactant volumes in gallons but need mass for stoichiometry or legal weight limits for transportation.
Common liquid densities and gal-to-kg factors
| Substance | Density (kg/L) | 1 US gal (kg) | 1 UK gal (kg) |
|---|---|---|---|
| Water | 0.998 | 3.782 | 4.543 |
| Sea Water | 1.025 | 3.882 | 4.660 |
| Milk | 1.032 | 3.908 | 4.692 |
| Honey | 1.420 | 5.377 | 6.455 |
| Heavy Cream | 0.994 | 3.764 | 4.518 |
| Wine | 0.995 | 3.768 | 4.523 |
| Beer | 1.005 | 3.806 | 4.568 |
| Olive Oil | 0.911 | 3.449 | 4.142 |
| Vegetable / Cooking Oil | 0.920 | 3.483 | 4.183 |
| Engine Oil | 0.875 | 3.312 | 3.978 |
| Crude Oil | 0.870 | 3.293 | 3.955 |
| Diesel | 0.832 | 3.150 | 3.783 |
| Gasoline | 0.737 | 2.790 | 3.351 |
| Kerosene | 0.800 | 3.028 | 3.637 |
| Jet Fuel | 0.804 | 3.043 | 3.655 |
| Bleach | 1.084 | 4.103 | 4.927 |
| Vinegar | 1.006 | 3.808 | 4.572 |
Approximate values at 20 degrees Celsius. US gallon = 3.7854 L, UK gallon = 4.5461 L.
Frequently asked questions
How many kilograms is 1 gallon of water?
One US gallon of water weighs approximately 3.782 kg (or 8.34 pounds) at room temperature. One UK (imperial) gallon of water weighs approximately 4.542 kg. The slight variation from a round number is because water density at 20 degrees Celsius is 0.9982 kg/L rather than exactly 1.0 kg/L.
How many kilograms is 1 gallon of milk?
One US gallon of milk weighs approximately 3.908 kg (about 8.62 pounds). Milk has a density of about 1.032 kg/L, which is slightly higher than water because of its dissolved solids (fat, protein, lactose and minerals). One UK gallon of milk weighs about 4.692 kg.
How many kg is 1 gallon of gasoline?
One US gallon of gasoline weighs approximately 2.79 kg (about 6.15 pounds). Gasoline is lighter than water, with a typical density around 0.737 kg/L. The exact value varies slightly with blend and temperature.
Is a gallon of water always 3.785 kg?
Almost. The 3.785 figure assumes the water density is exactly 1.000 kg/L, which is only true at 4 degrees Celsius. At 20 degrees Celsius (room temperature) water density is 0.9982 kg/L, giving 3.782 kg per US gallon. For practical purposes the difference is negligible, but this converter uses the more accurate density.
What is the difference between a US gallon and a UK gallon?
A US liquid gallon equals 3.785411784 liters. A UK (imperial) gallon equals 4.54609 liters. The UK gallon is about 20% larger. The same volume label means very different amounts depending on which country you are in, so it is important to confirm which type is intended when converting.
How do I convert kilograms back to gallons?
Divide the mass in kilograms by the density of the liquid in kg/L to get liters, then divide by the liters-per-gallon value (3.7854 for US or 4.5461 for UK). This calculator handles the reverse direction: just select "Kilograms to Gallons" in the Convert dropdown and enter the mass.