The formula
kg/m³ = g/cm³ × 1,000
Where the factor comes from — each unit by its definition, then its size in SI:
1 g/cm³ = g / cm³ = 1,000 kg/m³1 kg/m³ is the SI unit of density.
Dividing the two SI sizes gives the factor: 1,000, exact — every step above is a definition, not a measurement. The reverse factor is 0.001.
Density is mass per volume. 1 g/cm³ is exactly 1000 kg/m³ — water is close to that — and the buoyancy and pressure formulas take kg/m³.
Worked examples
- Water at room temperature (approximately): 1 g/cm³ = 1,000 kg/m³ — 1 × 1,000 = 1,000
- Typical structural steel: 7.85 g/cm³ = 7,850 kg/m³ — 7.85 × 1,000 = 7,850
- Air at sea level (ISA): 0.001225 g/cm³ = 1.225 kg/m³ — 0.001225 × 1,000 = 1.225
Frequently asked questions
How many kilograms per cubic metre is 1 g/cm³?
1 g/cm³ = 1,000 kg/m³, exactly, from the unit definitions.
How do I convert kilograms per cubic metre back to grams per cubic centimetre?
Divide by 1,000 — or multiply by 0.001: 1 kg/m³ = 0.001 g/cm³.