OD (Outside Diameter)

In detail

Outside Diameter (OD) is the precise measured distance across the external surface of a pipe, expressed in millimeters (mm) or inches. Unlike Nominal Bore, OD is an exact dimension that determines pipe fitment in flanges, fittings, and structural applications. Indian standards specify OD in mm (e.g., 48.3 mm, 60.3 mm), while American standards often use fractional inches. OD tolerance is typically ±0.4 mm for standard commercial pipes and tighter for precision applications.

Where you'll meet this in procurement

You will meet OD (Outside Diameter) on size charts, mill quotes, and fitment checks. Cross-check OD (Outside Diameter) against OD, wall thickness or schedule, length, and end finish so the delivered pipe matches flanges, fittings, and pressure duty—not just a familiar nominal label.

Related terms

• NB (Nominal Bore)Approximate internal diameter designation in inches for pipe sizing and selection.
• Wall Thickness (WT)The radial thickness of pipe material determining strength, weight, and pressure capacity.
• Tolerance ClassPermissible deviation from nominal dimensions, categorized as standard or precision grades.
• IS 3589BIS standard for steel pipes 168.3 mm to 2540 mm OD for water and sewage applications.

Related resources

• Pipe schedule chart
• Steel pipe weight calculator
• Request a quotation (RFQ)
• Back to full glossary