Return to FAQ's Index
FREQUENTLY ASKED QUESTIONS
What does SDR stand for?SDR is the Standard Dimension Ratio. Technically, it is the nominal outside diameter divided by the minimum wall thickness. The larger the SDR, the thinner the wall thickness. See tables (in ASTM F2160, D3485, NEMA TC7 or UL) for standard SDR numbers.
What is the SDR (SODR, SIDR)?SDR is the Size to Diameter Ratio (or Standard Dimension Ratio), that is, the ratio of the inside diameter (SIDR) or outside diameter (SODR) of the duct or innerduct to the wall thickness of the duct or innerduct. The smaller the SDR number the thicker the wall of the duct.
Smaller SDR numbers also mean that the duct or innerduct has higher tensile strength and greater crush resistance than a comparable product with a higher number.
Need help sizing conduit?The Conduit Design Calculator is a software tool that aids in determining the most appropriate wall thickness of high-density polyethylene (HDPE) conduit installed via horizontal directional drilling (HDD) techniques.