Mass to Volume Calculator

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About this tool

The conversion a unit converter has to refuse, done properly. Kilograms measure mass and litres measure volume, and nothing links them except the density of one specific substance - so you pick the substance, or type its density.

This is why "how many litres is a kilogram" has no general answer. A litre of water is a kilogram, which is where the intuition comes from and why it so often misleads: a litre of honey is about 1.42 kg, a litre of olive oil about 0.92, and a litre of flour barely 0.53. Using the water assumption on any of them is wrong by tens of per cent, and in the kitchen or on a delivery note that is the difference between a recipe working and not.

The substance list carries a density for each entry, and the awkward ones are exactly the common ones. Flour is the worst: its density depends on whether it was scooped, spooned or sifted, and the figure here is for lightly spooned flour, the convention most published recipes assume. Butter and honey vary with temperature. Where precision matters - baking especially - a scale beats any conversion, which is the honest recommendation even though it is not the answer this page exists to give.

Cups deserve their own warning. A Polish szklanka is 250 ml, a metric cup is 250 ml, a US customary cup is 236.6 ml and a US legal cup is 240 ml. Both American variants are on the list separately, because a recipe that says "cup" rarely says which one, and the difference across a multi-cup recipe is real.

Typing a density directly is available for anything not on the list: enter it in kg/m³, which is the same number as grams per litre. Everything is computed in your browser.

Good to know

Questions people actually ask

How many grams is a cup of flour?

About 132 g for a 250 ml cup of lightly spooned wheat flour - but the honest answer is that it depends on how the cup was filled. Scooping straight from the bag compacts the flour and can add 20 per cent; sifting removes about as much. For baking, weigh it: this is the one conversion where a scale genuinely beats arithmetic.

Why doesn't the unit converter do this?

Because mass and volume are different quantities and no factor connects them. A converter that turned kilograms into litres would have to assume a density, and assuming water would be wrong for honey by 42 per cent and for flour by nearly half. Refusing the conversion and pointing here is the correct behaviour, not a limitation.

Is a litre of water really exactly a kilogram?

Near enough for anything domestic. It was the original definition, and at 4 °C - water's densest point - it is exact. At room temperature a litre is about 998 g. The 0.2 per cent difference matters in a laboratory and nowhere else.

Which cup does this use?

Whichever you pick. A Polish szklanka and a metric cup are both 250 ml, a US customary cup is 236.6 ml, and a US legal cup is 240 ml. They are listed separately because recipes almost never say which they mean, and across several cups the difference adds up to a noticeable amount.

Can I use a substance that is not on the list?

Yes - choose the custom option and enter the density in kg/m³, which is numerically the same as grams per litre. Water is 1000, olive oil about 915, honey about 1420.