Site maths
Material mass & self-weight
- where
- mass (kg)
- volume (m³)
- bulk density (kg/m³)
- self-weight (kN)
Explain this equation
Gives the mass and self-weight of a known volume of material from its bulk density. Use it when planning handling, deliveries or skip loads, or when you need a dead load figure.
V is the volume in m³. ρ is the bulk density in kg/m³, which is how much one cubic metre weighs. m is the mass in kilograms, also shown in tonnes. F is the downward force that mass exerts, in kilonewtons.
Mass is volume times density. Weight is mass times gravitational acceleration, taken as 9.81 m/s², which gives newtons. Dividing by 1000 turns newtons into kilonewtons.
1 m³ at 1800 kg/m³ is 1800 kg, or 1.8 t, and about 17.7 kN. A handy rule is that each tonne weighs roughly 10 kN.
Watch out: wet and dry densities can differ a great deal. This gives a load, not a check on whether a floor or scaffold can carry it.
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
This is a calculation aid, not a structural design or compliance certificate. Every default is an example, not a specification for your project.