How this calculator works
Kilograms measure mass and litres measure volume, so the link between them is density. Volume equals mass divided by density. Water at about 4 °C has a density of nearly 1,000 kg/m3, which is 1 kg per litre, so 1 kg of water fills 1 L. Honey is denser, so a kilogram of honey fills a smaller volume, while gasoline is less dense and fills more. The presets are typical figures for each liquid, and the custom row accepts a measured density. Density changes with temperature, so a value taken at a different temperature will differ slightly.
Formula
litres = kilograms / density x 1,000, with density in kg/m3. Equivalently, litres = kilograms / (density in kg/L), where kg/L is the kg/m3 figure divided by 1,000. Millilitres are 1,000 times the litre value and US gallons are the litre value divided by 3.785411784.
Worked example
1 kg of water is 1 L. 1 kg of milk at 1,030 kg/m3 is 0.970874 L. 1 kg of honey at 1,420 kg/m3 is 0.704225 L. 1 kg of cooking oil at 920 kg/m3 is 1.08696 L. 5 kg of water is 5 L or 1.32086 US gallons. 1 lb of water is 0.453592 L.
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Frequently asked questions
Why is 1 kg not always 1 litre?
The two units measure different quantities. A kilogram is a mass and a litre is a volume, and the volume of a kilogram depends on how tightly the material packs. Only a liquid with a density close to 1,000 kg/m3, such as water, gives about 1 L per kg.
How exact is the 1 kg per litre figure for water?
Water reaches its maximum density near 4 °C at 999.97 kg/m3, and at 20 °C it is about 998.2 kg/m3. The preset uses 1,000 kg/m3, which is close enough for cooking and everyday use but not for calibration.
What density should I use for a liquid not listed?
Choose Custom density and enter the value from the product data sheet in kilograms per cubic metre. If a sheet gives grams per millilitre, the number is the same as kg/L, so multiply by 1,000 for kg/m3.
Does temperature change the answer?
Yes. Most liquids expand as they warm, so a litre holds slightly less mass at a higher temperature. The effect is small for water over room temperatures but noticeable for fuels and oils across a wide range.