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.
Common nominations are SDR11, SDR17 and SDR35. Pipes with a lower SDR can withstand higher pressures.
S D R = d o s {\displaystyle SDR={\frac {d_{o}}{s}}}
