Site maths
Material mass & self-weight
- where
- mass (kg)
- volume (m³)
- bulk density (kg/m³)
- force (kN)
Explain this equation
This works out the mass and self-weight of a known volume of material from its bulk density. Use it to estimate loads on a delivery, a skip or a structure.
V is the volume in m³ and ρ is the bulk density in kg/m³. m is the mass in kg. F is the weight in kilonewtons. The calculator also gives mass in tonnes.
Mass is volume times density. Weight is mass times gravity, taken as 9.81 m/s², which gives newtons; dividing by 1000 turns newtons into kilonewtons. One tonne is 1000 kg.
One cubic metre at 1800 kg/m³ is 1.8 tonnes and about 17.7 kN. A useful rule: each tonne weighs roughly 10 kN.
Watch out: use the right density for the material and its moisture. This does not check whether anything can carry the load.
Calculate mass and gravity load from a known volume and bulk density.
Enter your values to see the result.
Good to know
Use the correct dry/wet bulk density. This does not check floors, scaffolds, lifting operations or structural capacity.
Sources
- Geometry / arithmetic
Estimates are not design approval or British Standards compliance checks. Structural arch, retaining-wall, wind, foundation, lintel and masonry-capacity design are not performed. Use the project engineer’s specification.