A density calculator for g/cm³, kg/m³ and more
This density calculator solves the relationship ρ = m ÷ V for whichever quantity you do not know: density, mass or volume. Pick the unknown, enter the other two values with their units, and the answer appears at once together with the density in g/cm³, kg/m³ and lb/ft³, so you can compare it with a table in any textbook.
It is built for school physics and chemistry, for DIY and workshop estimates (“how heavy is this block of steel?”), and for checking unit conversions. Everything runs in your browser.
How to use the Density Calculator
- Choose what to solve for: Density, Mass or Volume.
- Enter the two known values and pick a unit for each (mg to tonnes, mm³ to US gallons, g/cm³ to lb/in³).
- Read the answer in your chosen unit in the large result box.
- Check the strip of conversions: density in g/cm³, kg/m³ and lb/ft³, plus mass in grams and volume in cm³.
- Use the water comparison line to see whether a solid of that density would float or sink.
Density Calculator features
Three modes
Density from mass and volume, mass from density and volume, or volume from mass and density.
Many units
Metric and US customary units for mass, volume and density, converted exactly through SI.
Instant conversions
The same density in g/cm³, kg/m³ and lb/ft³ without switching units.
Float or sink
A comparison with fresh water at 20 °C (about 998 kg/m³).
The density formula
Density is mass per unit volume: ρ = m / V. Rearranged, m = ρ × V and V = m / ρ. The SI unit is kilograms per cubic metre (kg/m³); chemists usually use grams per cubic centimetre (g/cm³), and 1 g/cm³ = 1 g/mL = 1 kg/L = 1000 kg/m³.
Worked example: a metal block has a mass of 270 g and a volume of 100 cm³. Its density is 270 ÷ 100 = 2.7 g/cm³, which is 2700 kg/m³ — about the density of aluminium. The same block would have a mass of 2.7 × 250 = 675 g if its volume were 250 cm³.
Typical densities (rounded, about 20 °C)
These are rounded reference values. Real samples differ with alloy, porosity and temperature, so use a measured value when accuracy matters.
| Material | g/cm³ | kg/m³ |
|---|---|---|
| Air (sea level) | 0.0012 | 1.2 |
| Ethanol | 0.79 | 789 |
| Water (fresh) | 1.00 | 998 |
| Aluminium | 2.70 | 2700 |
| Iron / steel | 7.85 | 7850 |
| Copper | 8.96 | 8960 |
| Lead | 11.34 | 11340 |
| Gold | 19.3 | 19300 |
Units and conversions
- 1 lb = 0.45359237 kg and 1 in = 0.0254 m (exact definitions), so 1 lb/ft³ ≈ 16.0185 kg/m³.
- 1 US gallon = 231 in³ = 3.785411784 L, and 1 L = 1000 cm³.
- Specific gravity is density divided by the density of water, so it has no unit; multiply by about 1000 kg/m³ to get density.
Tips for measuring density at home
- Weigh the object on a scale and note the unit; kitchen scales usually read grams.
- For an irregular solid, find the volume by water displacement: the rise in a measuring jug, in mL, equals the volume in cm³.
- Hollow or porous objects give an average density that is lower than the material itself, which is why a steel ship floats.
- Keep enough significant figures in the inputs: the answer cannot be more precise than the least precise measurement.
Related tools
Convert plain weights with the weight converter and volumes with the volume converter; the volume calculator finds the volume of common shapes to feed into this one.
Density Calculator FAQ
What is the density formula?
Density equals mass divided by volume, ρ = m/V. Mass is m = ρV and volume is V = m/ρ.
How do I calculate density in g/cm³?
Enter the mass in grams and the volume in cm³ (or mL) and keep the density unit at g/cm³. For example, 270 g in 100 cm³ gives 2.7 g/cm³.
How do I convert g/cm³ to kg/m³?
Multiply by 1000. Water at 1 g/cm³ is 1000 kg/m³.
Why does the water comparison say about 998 kg/m³?
Fresh water is densest near 4 °C (about 999.97 kg/m³); at 20 °C it is close to 998.2 kg/m³. The page uses 998.2 for the comparison.
Does temperature matter?
Yes. Most substances expand when heated, so density falls slightly; gases change a lot with temperature and pressure.
Can I find the mass of an object from its density?
Yes — choose Mass, enter the density and the volume, and the tool returns m = ρ × V in your chosen mass unit.