Mass per Volume
Density is how much mass is packed into a given volume — mass ÷ volume. The SI unit is kilograms per cubic meter (kg/m³). Water has a density of about 1,000 kg/m³ (or 1 g/cm³). Objects less dense than water float; denser ones sink.
Common Densities
| Material | Density (kg/m³) |
|---|---|
| Air (sea level) | ~1.2 |
| Water | 1,000 |
| Aluminum | 2,700 |
| Steel | 7,870 |
| Gold | 19,300 |
Converting Units
1 g/cm³ = 1,000 kg/m³ (both mass and volume scale, but the net ratio is 1,000). 1 kg/m³ = 0.0624 lb/ft³. These are fixed factors.