Pipe Weight Calculator

Pipe weight per foot is the area of the wall annulus times 12 inches times the material density. Since the annulus equals pi times the outer radius squared minus the inner radius squared, and the inner radius is the outer radius less the wall thickness, the expression collapses for carbon steel into the familiar shop formula: weight per foot equals 10.69 times the quantity outside diameter minus wall thickness, times wall thickness, with both in inches. A 4 inch nominal Schedule 40 pipe, 4.500 inch outside diameter with a 0.237 inch wall, comes to about 10.79 pounds per foot on that basis. The key convention is that outside diameter is fixed for a nominal pipe size while wall thickness varies with schedule, which is what allows the same threading dies, fittings and flanges to serve every schedule of a given size. Schedule 40 is the general purpose standard, Schedule 80 the extra strong wall, and higher numbers serve higher pressures. Internal capacity uses the inner diameter only, with 231 cubic inches per US gallon, so a 4 inch Schedule 40 line holds about 0.66 gallons per foot; water at 8.34 pounds per gallon can add more than the pipe itself weighs on large lines, which matters for hanger and support design. Calculated weights are theoretical. ASTM A53 permits the wall to run as much as 12.5 percent under nominal, and mill practice, coatings, linings and welded fittings all push actual weights away from the figure.

The dimensional system behind pipe schedules is an artifact of nineteenth century wrought iron practice. Early pipe was sized by its approximate bore, and Robert Briggs of the Pascal Iron Works in Philadelphia documented the manufacturing practice of the day around 1862, producing the dimensional and thread standard that became known as the Briggs standard and later American National Pipe Thread. As working pressures rose, mills thickened walls inward to preserve the outside diameter and the threads cut on it, so the nominal size drifted away from any actual dimension. That is why a 2 inch pipe is neither 2 inches inside nor outside, and why nominal pipe size is now purely a label. Wall thickness was originally described by the words Standard, Extra Strong and Double Extra Strong. The numbered schedule system replaced them in the late 1920s through the American Standards Association sectional committee that produced the B36 standards, with the schedule number approximating 1000 times the working pressure divided by the allowable stress. That work is the ancestor of ASME B36.10M for wrought steel pipe and B36.19M for stainless. Material specifications developed alongside it, with ASTM A53 covering welded and seamless black and galvanized steel pipe. The schedule concept was later carried over to plastics, where PVC pipe is dimensioned to the same Schedule 40 and 80 walls despite a density roughly one fifth that of steel.