Poisson’s Ratio Calculator
Find a material’s Poisson’s ratio, the measure of how much it narrows sideways when stretched lengthwise.
What Poisson’s ratio measures
Poisson’s ratio (ν) describes how much a material contracts sideways (transversely) when stretched lengthwise (axially), or bulges sideways when compressed. It is defined as ν = -(lateral strain / axial strain). Most common engineering materials have a Poisson’s ratio between about 0.2 and 0.5.
How this calculator works
Enter the lateral (transverse) strain and the axial (longitudinal) strain measured on a test sample. Strain values are typically negative when a dimension shrinks and positive when it grows — for a rod being stretched, axial strain is positive (it lengthens) and lateral strain is negative (it narrows). The calculator divides the two and flips the sign to give a positive Poisson’s ratio for typical materials.
A material with ν near 0.5 (like rubber) is nearly incompressible, while a value near 0 means it barely changes width when stretched. This calculator is for general engineering and educational purposes.