EngineerBenchCalculating round and rectangular tube weight
Tube mass comes from the material left between the outside and inside profiles. Choose round or rectangular tube, then enter outside dimensions, wall thickness, length, and density. The calculation subtracts the hollow area before multiplying by length; it does not treat the section as solid stock.
Use actual outside dimensions
A nominal pipe size is a designation and may not equal the measured outside diameter. Use the dimensions for the actual pipe or tube. Wall thickness must leave a positive internal opening in the selected geometry.
Why catalog weight can differ
The rectangular model uses square corners. Real hollow sections often have rounded corners, and stock has dimensional tolerances. Coatings and welded seams can also affect the measured mass. For a purchase or lifting plan, use the supplier's section data where available.
Subtracting the hollow cross-section
A round tube's material area is π divided by four times the difference between outside diameter squared and inside diameter squared. Inside diameter is outside diameter minus twice the wall thickness. Subtracting diameters before squaring is a different operation and gives the wrong area. The rectangular model similarly subtracts an inner rectangle from the outer one.
Multiply the resulting cross-sectional area by cut length and density to obtain mass. Keep the length conversion consistent with the area conversion: square millimeters multiplied by millimeters give cubic millimeters, not cubic meters. Longer pieces scale mass directly, but increasing wall thickness changes both internal dimensions and does not always scale area directly. Check proposed values against actual stock dimensions and manufacturing tolerances. If the tube has end plates, fittings, welded brackets, or contents, add their masses separately. The geometric estimate is useful for comparing sections, but a supplier's mass-per-length value is often a better basis for a particular purchased product.
Formula
Mass = (outer section area − inner section area) × length × density.