Standard dimension ratio (SDR) is a method of rating a pipe's durability against pressure. The standard dimension ratio describes the correlation between the pipe dimension and the thickness of the pipe wall. ^[1]

Common nominations are SDR11, SDR17, SDR26 and SDR35. Pipes with a lower SDR can withstand higher pressures.

${\displaystyle SDR={\frac {d_{o}}{s}}}$

${\displaystyle d_{o}}$ Pipe outside diameter

${\displaystyle s}$ Pipe wall thickness

References