Quick answer: density = mass ÷ volume. Rearranged: mass = density × volume and volume = mass ÷ density. Enter any two above — this calculator works in grams, cubic centimetres and g/cm³, where water is exactly 1.
The density triangle
These three are the same equation rearranged. The classic memory aid puts mass at the top of a triangle with density and volume below: cover the quantity you want, and the positions of the other two show whether to multiply or divide. Worked example — a 500 g aluminium block, density 2.70 g/cm³:
- Volume = mass ÷ density = 500 ÷ 2.70 = 185.2 cm³
- Check: 185.2 × 2.70 = 500 g ✓
Material densities
Look up a value to fill the density field. All in g/cm³ (equivalently kg/L); multiply by 1,000 for kg/m³:
| Material | g/cm³ | Material | g/cm³ |
|---|---|---|---|
| Balsa wood | 0.16 | Aluminium | 2.70 |
| Pine | 0.50 | Titanium | 4.51 |
| Ice | 0.92 | Steel | 7.85 |
| Water | 1.00 | Copper | 8.96 |
| Seawater | 1.025 | Silver | 10.49 |
| Magnesium | 1.74 | Lead | 11.34 |
| Concrete | 2.40 | Gold | 19.32 |
| Glass | 2.50 | Platinum | 21.45 |
Anything below 1 g/cm³ floats in water; anything above sinks. That is why ice floats (0.92), wood floats, and metals sink. For a fuller table across liquids, foods and aggregates, see the volume to weight calculator. The same principle is why board volume is quoted in litres — a surfboard volume calculator is really asking how much water the board must displace to float your body weight.
Frequently asked questions
What is the density formula?
Density = mass ÷ volume. Rearranged, mass = density × volume, and volume = mass ÷ density. These three forms are often drawn as a triangle with mass on top and density and volume below, so you can cover the quantity you want and read off the formula.
How do I find volume from mass and density?
Divide mass by density: volume = mass ÷ density. A 500 g block of aluminium at 2.7 g/cm³ has a volume of 500 ÷ 2.7 ≈ 185 cm³. Make sure the mass and density units are compatible — grams with g/cm³, kilograms with kg/m³.
What are the units of density?
Common units are grams per cubic centimetre (g/cm³) and kilograms per cubic metre (kg/m³). They relate simply: 1 g/cm³ = 1,000 kg/m³. Water is 1 g/cm³ or 1,000 kg/m³, which is the reference point most other densities are compared against.
Why does water have a density of 1?
Because the metric system was designed that way. A gram was originally defined as the mass of one cubic centimetre of water, making its density exactly 1 g/cm³. Anything with a density below 1 g/cm³ floats in water, and anything above sinks.
Does density change with temperature?
Yes, slightly. Most materials expand as they warm, so their density falls a little. Water is densest at 4 °C. For everyday calculations the effect is negligible, but it matters in precise laboratory and engineering work, where density is quoted at a standard temperature.