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Density is how much mass is packed into a given volume — the reason a small lump of lead outweighs a large block of foam. This calculator uses the relationship density = mass ÷ volume and solves for whichever of the three you don’t know.
How is it calculated?
One relationship, three forms
ρ = m ÷ V
Rearranged for whichever quantity is unknown:
| Solve for | Formula |
|---|---|
| Density | ρ = m ÷ V |
| Mass | m = ρ × V |
| Volume | V = m ÷ ρ |
Units are yours to choose
Density has no single unit — it depends on what you put in. Grams and cubic centimetres give g/cm³ (the common lab unit, where water is 1); kilograms and cubic metres give kg/m³ (where water is 1000). Keep your inputs in a consistent system and the answer follows.
Where it’s used
Identifying materials, checking whether something floats (denser than the fluid sinks), converting between weight and volume of a substance, and countless problems in chemistry, physics and engineering.
Worked example
A metal block has a mass of 54 g and a volume of 20 cm³. Its density is 54 ÷ 20 = 2.7 g/cm³ — which happens to be aluminium. Turn it around: if you know a liquid’s density is 0.8 g/cm³ and you have 500 cm³ of it, the mass is 0.8 × 500 = 400 g.
FAQ
How do I calculate density?+
Divide mass by volume: density = mass ÷ volume. A 54 g object occupying 20 cm³ has a density of 2.7 g/cm³. Choose “Density” mode and enter the mass and volume.
How do I find mass or volume instead?+
Rearrange the same relationship. Mass = density × volume; volume = mass ÷ density. The calculator does this — pick which quantity is unknown and enter the other two.
What units should I use?+
Any consistent set. Grams with cubic centimetres give g/cm³ (water ≈ 1), kilograms with cubic metres give kg/m³ (water ≈ 1000). The result’s unit is determined by the units you enter.
What is the density of water?+
About 1 g/cm³ (or 1000 kg/m³) at room temperature. It’s the reference point: substances denser than water sink in it, and less dense ones float.
How does density relate to floating?+
An object floats in a fluid if it is less dense than that fluid, and sinks if it is denser. That’s why ice (slightly less dense than liquid water) floats, and why a steel ship floats only because its overall average density, hollow inside, is low.