Density links volume and mass
Estimated tonnes = volume in m³ × bulk density in tonnes per m³.
Bulk density varies
Material grading, particle shape and moisture can change the bulk density. Decorative gravel, sand, MOT Type 1 and topsoil should not all use the same figure.
Use the supplier figure where possible
If the merchant publishes a density or coverage for the exact product, use that figure in the calculator.
Compaction is a separate issue
A compacted layer depth and a loose delivered volume are not automatically interchangeable. Follow the project and supplier guidance for the intended use.
Use the numbers in a calculator
Accuracy note
Where a figure depends on a product, supplier, installation method or project specification, use the current information for the exact material being purchased. The reference pages explain the maths and estimating logic; they are not a substitute for current technical data.