What this calculator does
Converting litres to kg only has one right answer once you know what you are measuring. A litre of water weighs almost exactly 1 kg, but a litre of milk weighs a bit more, and a litre of cooking oil weighs a bit less, because kilograms measure mass and litres measure volume, and the two are only tied together by density.
This calculator asks for that density directly, so it works for any liquid or bulk material rather than assuming everything behaves like water. Enter the density in kilograms per litre, in either direction, and it converts kg to litres or litres to kg using that figure.
The formula
Litres are found by dividing the mass in kg by the density in kg/L. Kg is found by multiplying the volume in litres by that same density. Density itself has to come from somewhere: a food label, a materials data sheet, or a known reference value for the substance.
| Term | Meaning |
|---|---|
| Density | Mass per unit volume, in kilograms per litre. Water is almost exactly 1.00 kg/L at room temperature. |
| Litres | A measure of volume: how much space the substance takes up. |
| Kilograms | A measure of mass: how much matter is present, independent of volume. |
The inputs explained
| Field | What to enter |
|---|---|
| Value | The kg or litre value you already have, depending on which direction you are converting. |
| Convert | Whether you are converting kg to litres, or litres to kg. |
| Density (kg/L) | The density of the substance in kg per litre. Water is close to 1.00; milk is around 1.03; cooking oil is around 0.92; honey is around 1.42; petrol is around 0.74; diesel is around 0.85. Use the actual figure for your substance where you have one. |
When to use it
Converting a recipe or ingredient quantity
A recipe or supplier spec sometimes gives a liquid ingredient by weight and sometimes by volume; converting between them needs the ingredient’s own density, not water’s, once it is anything other than water.
Working out fuel or chemical quantities
Fuels, oils and industrial liquids are usually priced or dosed by volume but limited by weight for transport or storage, so converting reliably between the two matters for both cost and compliance.
Checking a labelled weight against a container size
A container marked in litres but sold by weight, or the reverse, can be cross-checked against the substance’s density to confirm the numbers are consistent.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How much does 1 litre weigh for different substances?
The same 1 litre volume, at densities for a few common substances.
| Substance (density) | Kilograms |
|---|---|
| Petrol (0.74 kg/L) | 0.740 kg |
| Diesel (0.85 kg/L) | 0.850 kg |
| Cooking oil (0.92 kg/L) | 0.920 kg |
| Water (1.00 kg/L) | 1.000 kg |
| Milk (1.03 kg/L) | 1.030 kg |
| Honey (1.42 kg/L) | 1.420 kg |
Kg to litres of water at increasing weights
A range of kg amounts of water, converted to litres.
Questions
Is 1 kg always equal to 1 litre?
Only for water at around room temperature, where density is very close to 1.00 kg/L. For any other substance the two figures diverge, sometimes considerably, so kg and litres should not be swapped without checking density first.
Where do I find the density of a substance?
Food packaging, safety data sheets and materials references usually list density directly, often as kg/L, g/mL or g/cm³ (all the same numeric value, since 1 g/mL equals 1 kg/L). If none is available, weighing a known volume gives you a working figure.
Does temperature affect this conversion?
Yes, density itself changes slightly with temperature, since most liquids expand a little as they warm. For everyday conversions the effect is small enough to ignore; for precise industrial or scientific work, use a density figure measured at the relevant temperature.
Why does milk weigh more than water?
Milk contains dissolved and suspended solids, fat, protein and sugars, on top of the water itself, which pushes its density slightly above 1.00 kg/L, typically to around 1.03 kg/L.
For density values in units other than kg/L, see the density unit converter. For converting mL to grams for kitchen liquids specifically, see the mL to grams converter.