Mass to volume needs one extra number: density
You cannot convert kilograms straight to millilitres. Mass is how much matter there is; volume is how much space it takes. Density — grams per millilitre — links the two. Water sits at 1.000 g/mL, which is why 1 kg of water is exactly 1,000 mL and everything else is measured against it.
Density of common substances (at 20°C)
Pick the density for your material, then divide 1,000 grams per kilogram by it. Denser than water (honey) gives fewer millilitres per kg; lighter (oil, flour) gives more.
| Substance | Density (g/mL) | 1 kg = |
|---|---|---|
| Water | 1.000 | 1,000 mL |
| Whole milk | 1.030 | 971 mL |
| Olive oil | 0.920 | 1,087 mL |
| Honey | 1.420 | 704 mL |
| Wheat flour | 0.593 | 1,686 mL |
Milk is heavier than water because of its fat, protein and sugar; oil and flour are lighter, so the same kilogram fills more space.
What throws the number off
- Temperature. Liquids expand when warm, so density drops about 0.2–0.5% per 10°C. Use the 20°C figure for kitchen work unless the liquid is hot.
- Packing. Sifted flour is less dense than scooped, packed flour, so the table value is a guide, not a guarantee.
- Purity and mix. A sugar syrup climbs from 1.04 g/mL at 10% sugar to about 1.45 at full saturation, changing the volume a lot.
Common questions
Can I convert kg to mL without knowing the substance?
No. Kilograms measure mass and millilitres measure volume, which are different things. You need the density of the material to bridge them. One kilogram of water is 1,000 mL, but one kilogram of flour is closer to 1,686 mL because flour is less dense.
What is the formula?
Volume in mL equals mass in kg times 1,000, divided by density in g/mL. For water the density is 1, so the 1,000 comes straight through: 0.5 kg of water is 500 mL.
Why does my result differ from another calculator?
Almost always the density value. The same substance shifts with temperature, moisture and purity, so one tool may use 0.593 for flour and another 0.59. Warmer liquids are also slightly less dense, which changes the volume by a few tenths of a percent per 10 degrees.
