# Standard Dimension Ratio

Standard Dimension Ratio (SDR) is a key figure commonly used to classify PE , PP and other plastic pipes , which shows the ratio between the outer diameter and the wall thickness of a pipe:${\ displaystyle \ mathrm {SDR} = {\ frac {d_ {a}} {s}}}$

Outer pipe diameter: ${\ displaystyle d_ {a}}$

Pipe wall thickness: s

The SDR number is used to indicate the pressure resistance; to ensure a certain pressure resistance, a certain SDR number is necessary depending on the type of material. The following applies:

The greater the wall thickness, the smaller the SDR number and the more pressure-resistant the pipe.

The following SDR numbers are common:

• SDR 5 (corresponds to pipe series S2, PN40 for PE 100 )
• SDR 7.4 (corresponds to pipe series S3.2, PN25 for PE 100)
• SDR 11 (corresponds to pipe series S5, PN16 for PE 100)
• SDR 13.6 (corresponds to pipe series S6.3, PN12.5 for PE 100)
• SDR 17 (corresponds to pipe series S8, PN10 for PE 100)
• SDR 17.6
• SDR 26 (corresponds to pipe series S12.5, PN4 for PE 100)
• SDR 33