What this converter does
This density converter turns pounds per cubic foot into kilograms per cubic metre and back instantly. It covers the densities used in construction — g/cm³, t/m³, kN/m³ and lb/in³ — with exact factors, so every result is precise. Enter a value and read the answer as you type.
Converting US density figures to SI is routine when checking specs against metric codes or mix designs. For material strength rather than density, try the psi to MPa converter.
The units it covers
Every unit here is a mass per unit volume, so each converts through the kilogram per cubic metre with a fixed ratio.
View all units & their values
| Unit | Symbol | Value | Mainly used |
|---|---|---|---|
| Kilogram per cubic metre | kg/m³ | 1 | SI density — concrete, soil, steel |
| Pound per cubic foot | lb/ft³ | 16.018 | US construction densities |
| Gram per cubic centimetre | g/cm³ | 1000 | Lab values, specific gravity |
| Tonne per cubic metre | t/m³ | 1000 | Bulk materials, aggregates |
| Kilonewton per cubic metre | kN/m³ | 101.97 | Unit weight in geotech design |
| Pound per cubic inch | lb/in³ | 27679.9 | Metals, dense materials |
The formula
Each unit has a fixed value in kg/m³, so converting between any two means passing through that base once:
result = value × factor_from ÷ factor_toWhere:
- value = the number you typed, in the “from” unit
- factor_from = the “from” unit’s value in kg/m³
- factor_to = the “to” unit’s value in kg/m³
Worked example
Convert 150 lb/ft³ (typical concrete) to kg/m³.
1 lb/ft³ = 16.018463 kg/m³150 × 16.018463 = 2402.8 kg/m³So 150 lb/ft³ concrete is about 2400 kg/m³.
The units in this example
The US customary density unit — pounds of mass per cubic foot. Common in American construction specs and material data sheets.
- 1 lb/ft³ = 16.018 kg/m³
- Water ≈ 62.4 lb/ft³
- Concrete ≈ 150 lb/ft³
- Steel ≈ 490 lb/ft³
The SI unit of density — mass in kilograms per cubic metre. Standard for concrete, soil and material densities across most of the world.
- 1 kg/m³ = 0.0624 lb/ft³
- 1000 kg/m³ = 1 g/cm³
- 1000 kg/m³ = 1 t/m³
- Water ≈ 1000 kg/m³