Calculate the weight of a metal bar, plate, or sheet from its dimensions and material — steel, aluminum, copper, brass, iron, or stainless.
weight = length × width × thickness × density
Weight is the volume in cubic inches times the material's density. Steel is 0.2836 lb/in³, aluminum 0.0975, copper 0.3230.
Aluminum is about a third the weight of steel for the same size — always pick the right material.
A 12 x 12 x 0.25 inch plate is 36 cubic inches. In steel (0.2836 lb/in³) it weighs 36 x 0.2836 = 10.2 lb. The identical plate in aluminum (0.0975 lb/in³) weighs only 3.5 lb — about a third — which is exactly why aluminum is chosen where weight matters.
For shipping, fabrication, or structural load, knowing the weight up front prevents surprises. Multiply by the number of pieces for a batch: ten of those steel plates is 102 lb.
Densities are standard engineering-handbook values for common metals. Alloy variations shift these slightly.
A 12×12×0.25″ steel plate weighs about 10.2 lb — 36 in³ at 0.2836 lb/in³.