Steel Weight Calculator

The weight of any prismatic metal section is cross-sectional area times length times density, and all the work is in the area term. A round bar is pi times radius squared. A square bar is the side squared. A flat bar is width times thickness. A tube is the annulus, pi times (outer radius squared minus inner radius squared), where the inner radius is the outer radius less the wall thickness. An equal-leg angle is approximated as two legs minus their overlapping corner, or (2 times leg times thickness) minus thickness squared, which slightly overstates a hot-rolled angle because the real section has a filleted root. Density then converts volume to mass: 0.2836 lb per cubic inch for carbon steel, 0.289 for 304 and 316 stainless, 0.0975 for 6061 aluminum and 0.323 for copper. Useful anchors: a 1 in diameter carbon steel round bar is 2.67 lb per foot and a 2 in round is 10.68 lb per foot, since weight scales with the square of diameter and doubling the size quadruples the mass. Aluminum 6061 lands near 34 percent of steel weight for identical geometry, which is why material choice often matters more than section choice for handling. These are theoretical weights. Hot-rolled bar is produced to tolerances that usually leave it slightly over nominal, cold-drawn stock sits closer to nominal, and pipe is a special case because nominal pipe size is not the outside diameter - 2 in schedule 40 pipe measures 2.375 in outside with a 0.154 in wall. Expect 2 to 5 percent spread between calculated and weighed pieces.

Quoting metal by weight rather than by piece is a legacy of how mills sell and how freight is priced. Once rolling mills could produce standard sections in continuous lengths, theoretical pounds per foot became the natural unit for both pricing and structural design, and handbook tables giving weights for rounds, squares, flats, angles and tubes appeared in the late nineteenth century alongside the rapid growth of structural steel framing in American cities. The density constants rest on older metrology: the accepted 7850 kg per cubic meter for structural carbon steel reflects pure iron near 7874 kg per cubic meter adjusted for carbon and alloy content, and the displacement method for measuring specific gravity goes back to Archimedes. Standardization of the shapes themselves came through the mill catalogs of Carnegie Steel and its successors and then through the American Institute of Steel Construction, whose 1927 manual consolidated competing catalogs into a common set of sections and properties, while ASTM took responsibility for material specifications. Aluminum joined the list far later, because only the Hall-Heroult electrolytic smelting process, developed independently by Charles Martin Hall and Paul Heroult in 1886, made the metal cheap enough to compete; the 6061 alloy used for most extruded bar and tube dates from the 1930s.