The formula
Weight per metre = (OD − wall thickness) × wall thickness × density factor. With OD and wall thickness in millimetres and carbon steel at 7850 kg/m³, the factor works out to 0.02466, giving weight directly in kg/m.
- W (kg/m) = (OD − t) × t × 0.02466 for carbon steel
- Stainless steel is roughly 2% heavier (about 8000 kg/m³)
- Multiply kg/m by the length in metres for total weight
Worked example
Take NPS 4 SCH 40 carbon steel pipe: OD 114.3 mm, wall 6.02 mm. (114.3 − 6.02) × 6.02 × 0.02466 = 16.07 kg/m. A 6 m length therefore weighs approximately 96.4 kg.
Why calculated and actual weight differ
Calculated weight is theoretical. Mill tolerances on wall thickness and outside diameter, plus any coating, mean delivered weight can vary from the calculation. Commercial weight is normally settled against the applicable product standard's tolerance.
Common questions
- What density should I use for mild steel pipe?
- 7850 kg/m³ is the value normally used for carbon and mild steel. Stainless grades are usually taken as about 8000 kg/m³.
- Does the formula work for square and rectangular sections?
- No. That formula is specific to round hollow sections. Square and rectangular hollow sections use a perimeter-based calculation that also accounts for corner radii.
Next step
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