The formula
where t is wall thickness and OD is outside diameter, both in millimetres. This is derived from the pipe's annular cross-sectional area (a ring, not a solid circle) multiplied by steel density (7,850 kg/m³) — a 4″ OD (114.3mm) pipe with a 6mm wall works out to about 16.0 kg/m, matching published schedule-40-range pipe weight tables.
Reading the result alongside bore size
The calculator also reports approximate internal bore (OD minus twice the wall thickness), which is useful for a quick sanity check against flow capacity or fitting compatibility, though it isn't a substitute for checking the exact schedule/class dimensions on a manufacturer's data sheet.
Frequently asked questions
Does this work for any pipe schedule (Sch 40, Sch 80, etc.)?
Yes — schedule numbers just correspond to specific OD/wall-thickness combinations. Enter the actual OD and wall thickness for your schedule and the formula gives the correct weight regardless of the schedule label.
What steel density does this use?
7,850 kg/m³, the standard reference density for carbon steel pipe.
Is this accurate for stainless steel pipe?
Not exactly — stainless steel is slightly denser (around 7,900-8,000 kg/m³ depending on grade) than the 7,850 kg/m³ used here for carbon steel, so results will be a few percent light. Fine for estimating; check the mill certificate for precise stainless weights.