Density Converter
Convert kg/m³ to g/cm³ and lb/ft³ — plus g/mL and kg/L — instantly. Type any value to update every field at once.
- Water = 1,000 kg/m³ = 1 g/cm³ = 62.43 lb/ft³. This is the reference density everything else is compared to.
- g/cm³ → kg/m³: multiply by 1,000. So steel at 7.85 g/cm³ = 7,850 kg/m³.
- lb/ft³ → kg/m³: multiply by 16.0185. Concrete at 150 lb/ft³ ≈ 2,403 kg/m³.
- g/cm³, g/mL and kg/L are numerically identical — three notations for the same density.
- Specific gravity = density ÷ 1,000 kg/m³. Below 1 floats, above 1 sinks; gold is 19.32.
What is the density of water in kg/m³?
Pure water at 4°C has a density of 1,000 kg/m³, which is exactly 1 g/cm³, 1 g/mL and 1 kg/L. That neat round value is not a coincidence — the kilogram and the litre were originally defined so that one litre of water would weigh one kilogram. At room temperature (20°C) water is fractionally less dense at about 998.2 kg/m³, and sea water averages roughly 1,025 kg/m³ because of dissolved salts, which is why it is slightly easier to float in the sea than in a pool.
Water matters here because it is the yardstick for specific gravity — a material's density divided by the density of water. A specific gravity below 1 means the material floats; above 1 means it sinks. That is why ice (about 917 kg/m³) floats while a steel bar (7,850 kg/m³) drops straight to the bottom.
How do I convert g/cm³ to kg/m³?
Multiply g/cm³ by 1,000 to get kg/m³. So iron at 7.874 g/cm³ is 7,874 kg/m³, and aluminium at 2.70 g/cm³ is 2,700 kg/m³. The factor is exactly 1,000 because a gram is one-thousandth of a kilogram while a cubic centimetre is one-millionth of a cubic metre — the two scaling factors combine to a clean ×1,000. This is the single most useful density conversion because scientific data sheets tend to quote g/cm³ while engineering calculations use kg/m³.
How do I convert lb/ft³ to kg/m³?
Multiply lb/ft³ by 16.0185 to get kg/m³, or multiply kg/m³ by 0.062428 to go the other way. As a worked example you can check against the tool, type 7.85 into the g/cm³ field: the converter returns 7,850 kg/m³, 490.06 lb/ft³, 0.28360 lb/in³ and 7.8676 oz/fl oz — the density of structural steel. Imperial density units are common in US-origin material specifications, so this conversion comes up whenever UK engineers work from American data.
What are the densities of common materials?
The table below lists reference densities for everyday materials in all three common notations. Every row can be reproduced in the converter above by typing the kg/m³ value into its field and reading the rest — a fast way to move a data-sheet figure into whichever unit your calculation needs.
| Material | kg/m³ | g/cm³ | lb/ft³ |
|---|---|---|---|
| Water (4°C) | 1,000 | 1.000 | 62.43 |
| Air (15°C, sea level) | 1.225 | 0.001225 | 0.0765 |
| Aluminium | 2,700 | 2.70 | 168.6 |
| Steel | 7,850 | 7.85 | 490.0 |
| Concrete | 2,400 | 2.40 | 149.8 |
| Oak wood | 720 | 0.72 | 44.96 |
| Gold | 19,320 | 19.32 | 1,206 |
Density links mass and volume: mass = density × volume. So half a cubic metre of concrete at 2,400 kg/m³ weighs 1,200 kg, and a litre of petrol at about 745 kg/m³ weighs roughly 0.75 kg. To move between the mass and volume figures those calculations need, pair this with the mass converter and the volume converter.
Why are g/cm³, g/mL and kg/L all the same?
They are the same because 1 cm³ = 1 mL exactly, and 1 kg per litre resolves to the identical ratio, so 1 g/cm³ = 1 g/mL = 1 kg/L = 1,000 kg/m³. The choice between them is purely conventional: chemists write g/mL for solutions, engineers write g/cm³ for solid materials, and logistics or fuel contexts use kg/L. Whichever your source uses, the number in front of the unit is the same — only kg/m³ differs, by a factor of exactly 1,000.
The one imperial-style field to treat with care is oz/fl oz (UK), which is not exactly 1 for water. A UK fluid ounce is 28.413 mL while an avoirdupois ounce is 28.350 g, so water comes out at about 0.9977 oz/fl oz rather than a clean 1 — a reminder that imperial "same-name" mass and volume units rarely cancel as neatly as metric ones. For pressures and stresses that depend on material density, see the pressure converter.
Density conversion FAQs
Pure water at 4°C has a density of 1,000 kg/m³, which equals exactly 1 g/cm³, 1 g/mL and 1 kg/L. At room temperature (20°C) it is slightly less dense at about 998.2 kg/m³, and sea water averages around 1,025 kg/m³ because of dissolved salts.
Multiply g/cm³ by 1,000 to get kg/m³. So iron at 7.874 g/cm³ = 7,874 kg/m³. The factor is exactly 1,000 because a gram is one-thousandth of a kilogram and a cubic centimetre is one-millionth of a cubic metre, and those factors combine to ×1,000.
Multiply lb/ft³ by 16.0185 to get kg/m³. So concrete at about 150 lb/ft³ = 2,403 kg/m³. To go the other way, multiply kg/m³ by 0.062428 to get lb/ft³, so water at 1,000 kg/m³ is 62.43 lb/ft³.
Because 1 cm³ = 1 mL exactly, and 1 kg/L works out to the same ratio, so 1 g/cm³ = 1 g/mL = 1 kg/L = 1,000 kg/m³. They are three notations for one density, chosen by field: chemistry favours g/mL, engineering g/cm³ and logistics kg/L.
Dry air at sea level and 15°C has a density of about 1.225 kg/m³ (0.001225 g/cm³). This is the standard-atmosphere value used in aviation and fluid dynamics. Warm or humid air is slightly less dense, which is why hot-air balloons rise.
Steel is about 7,850 kg/m³ (7.85 g/cm³ or 490 lb/ft³) and aluminium about 2,700 kg/m³ (2.70 g/cm³ or 169 lb/ft³). Aluminium is roughly a third the density of steel, which is why it is used where weight matters, such as aircraft.
Multiply density by volume: mass = density × volume. So 0.5 m³ of concrete at 2,400 kg/m³ weighs 1,200 kg. Keep units consistent — use kg/m³ with m³, or g/cm³ with cm³ — and this converter puts any density into the unit that matches your volume.
Specific gravity is a material's density divided by the density of water (1,000 kg/m³), so it is a dimensionless number. Steel's specific gravity is about 7.85 and gold's about 19.32. Anything with a specific gravity below 1 floats on water; above 1 it sinks.
Convert kilograms, stone, pounds, tonnes and ounces — the mass side of density.
Convert litres, cubic metres, millilitres, gallons and cubic feet, both ways.
Convert Pascals, bar, psi and atmospheres for fluids and materials.