N/m³

newton per cubic meter

Unit weightexact by definition

The newton per cubic metre is the SI unit of specific weight, the weight of a unit volume of material. Its factor is 1 by construction. Specific weight is density times gravitational acceleration, so water at 1000 kg/m³ has a specific weight of about 9807 N/m³ under standard gravity.

Watch out: Specific weight is a force per volume and depends on gravity, while density is a mass per volume and does not. On the Moon a material's density is unchanged but its specific weight falls by a factor of six. Geotechnical practice calls this the unit weight and uses it heavily, since soil pressures come from weight rather than mass.

1 N/m³ 0.001 kN/m³