MachineCalcs

Pipe Weight Formula

Pipe weight uses the annulus area: outside circle minus inside circle. Nominal pipe size is not the actual outside diameter, so use the pipe schedule chart when converting NPS and schedule to OD and wall thickness.

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Pipe and tube formula

Round pipe is a hollow circle. If OD is outside diameter and t is wall thickness, the inside diameter is ID = OD - 2t. The metal area is: A = π/4 · (OD² - ID²) Then weight (kg) = ρ · A · L / 1,000,000 with density in g/cm³ and dimensions in mm.

For weight per metre, use kg/m = ρ · A / 1000. For mild steel, ρ = 7.85 g/cm³.

Worked example: 2 inch schedule 40 steel pipe

NPS 2 schedule 40 pipe has OD = 60.3 mm and wall t = 3.91 mm, so ID = 52.48 mm. The annulus area is 692.7 mm². Weight per metre is 7.85 × 692.7 / 1000 = 5.44 kg/m, and a 6 m length weighs about 32.6 kg.

Nominal pipe size versus actual diameter

NPS is a nominal trade size. A "2 inch" steel pipe is not 2 inches outside diameter; its actual OD is 2.375 in (60.3 mm). The outside diameter stays fixed for an NPS size, while schedule changes the wall thickness and inside diameter. Use the steel pipe schedule chart for those inputs.

Pipe versus mechanical tube

Pipe is usually ordered by NPS and schedule. Mechanical tube is usually ordered by actual OD and wall thickness. Once you have OD and wall, the weight formula is identical for both. Coatings, seam weld reinforcement and mill tolerances can move real shipped weight slightly from the nominal calculation.

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Last reviewed: June 1, 2026.