Size vs Pipe O.D. FAQs
DN (Diameter Nominal)
mm and inch are used often as well
Is it true that for DN XX pipe, pipe outer diameter (O.D.) is XXmm?
G.I. / Black Steel Pipe
Not always. For instance, pipe O.D. of DN15 1/2" pipe is not 15mm; while for size DN350 14" and above, size equals to pipe O.D.
Ductile Iron Pipe
D.I. pipe size is different from pipe O.D. in any size.