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