The minimum bend radius is expressed as a multiple of which pipe dimension?

• A. Inside diameter
• B. Outside diameter
• C. Wall thickness
• D. Length

Answer: (B)

Bend radius is standardized using a multiple of the pipe’s outside diameter because OD is the consistent external size of the pipe that doesn’t vary with wall thickness. Since wall thickness (schedule) changes, using the inside diameter would make the bend tightness depend on thickness, leading to inconsistent allowances across different pipes. Referencing the bend radius to the outside diameter gives a uniform, fabrication-friendly standard that also matches how fittings and supports are sized. So a stated minimum bend radius scales with the pipe’s overall external size, not with its inner bore.