Rectangular Cuboid Weight Calculator

This calculator estimates the mass of a solid rectangular cuboid from its length, width, height and density. Each dimension can use a different supported unit; the page converts all three to metres, calculates cubic metres, then multiplies by density in kilograms per cubic metre. Although the page name says weight, the numerical result is mass in kilograms. Weight as a force would also depend on gravitational acceleration.

1. Enter positive length, width and height measurements. Select centimetres, metres, inches, feet or yards beside each value.
2. Enter the material’s density in kg/m³. Use a value for the actual material, temperature, moisture condition and composition when those details matter.
3. Select Calculate. The page converts dimensions to metres, multiplies them for volume, and multiplies volume by density for mass.

The formula assumes a completely solid, uniform rectangular shape. For a hollow box, layered assembly, holes or several materials, calculate each solid region separately and add or subtract the appropriate masses.

The mass estimate is only as accurate as the dimensions and density. Nominal lumber, sheet and block sizes may differ from actual dimensions. Published density values are often representative rather than guaranteed; wood moisture, alloy, porosity, temperature and manufacturing variation can all matter. Use supplier data or a measured sample for decisions sensitive to load.

A hollow rectangular container cannot be modeled by entering its outside dimensions with the wall material density because that treats the interior as solid. Find outside volume minus inside void volume, or calculate each wall. For a filled container, calculate container and contents separately with their own densities.

Do not use the mass result alone to approve lifting, transport, storage or structural support. Equipment limits can depend on load distribution, centre of gravity, dynamic forces and safety factors. Preserve measurement precision through conversion and round only the final estimate to a sensible number of significant figures.

Mixed-unit entries are useful but deserve a rough sense check. A 100 cm edge, a 1 m edge and a 39.37 in edge are all about one metre. If replacing one with another changes volume greatly, a selector or decimal is probably wrong. Volume changes in direct proportion to any one dimension, so doubling only length doubles both volume and mass. Doubling all three dimensions multiplies volume and mass by eight. These scaling checks help detect errors before a heavy item is lifted, shipped or supported, although they do not replace a measured mass for critical work. Label every intermediate volume and mass with its unit so conversion mistakes remain visible.