Size to Weight Calculator (Rectangular Box)

The method

weight = cross-sectional area × length × density

Area first, then length

Every one of these is the same calculation: work out the cross-section, multiply by the length to get a volume, multiply by density to get a weight. What differs is only the geometry of the section.

For a pipe the section is the ring between the outside and inside diameters, π/4 × (OD² − ID²). Using the outside diameter alone treats the pipe as a solid bar and gives a wildly high answer, which is the usual mistake.

Densities are nominal. Steel varies a little with alloy, and rolled sections carry mill tolerances of a few per cent, so treat the figure as close rather than exact — for anything being lifted, use the mill certificate.