Enter transverse strain and axial strain to calculate Poisson's Ratio — or switch to the modulus method and input Young's modulus and shear modulus to get the same result. The calculator returns the dimensionless Poisson's ratio (ν) that describes how a material deforms laterally under axial stress.
Poisson's Ratio (ν)
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Material Category
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Transverse Strain
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Axial Strain
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Poisson's ratio (ν) is a dimensionless material property that describes how much a material deforms in directions perpendicular to an applied load. It is defined as the negative ratio of transverse strain to axial (longitudinal) strain. Most common engineering materials have a Poisson's ratio between 0 and 0.5.
Using strains: ν = −ε_transverse / ε_axial, where ε_transverse is the lateral strain and ε_axial is the strain in the load direction. Alternatively, using elastic moduli: ν = E / (2G) − 1, where E is Young's modulus and G is the shear modulus.
Yes, although it is rare. Materials with a negative Poisson's ratio are called auxetic materials — they actually expand laterally when stretched. Examples include certain foams, honeycombs, and engineered metamaterials. Most natural materials have positive Poisson's ratios.
Rubber typically has a Poisson's ratio close to 0.5 (nearly incompressible). Steel is around 0.28–0.30, aluminum is about 0.33, concrete is roughly 0.1–0.2, and cork is close to 0, meaning it barely expands laterally when compressed. This is why cork works so well as a bottle stopper.
For isotropic materials, Poisson's ratio must lie between −1 and 0.5 to satisfy thermodynamic stability conditions. A value of 0.5 corresponds to a perfectly incompressible material (like rubber), while −1 represents a theoretical lower limit for auxetic materials.
Temperature can influence Poisson's ratio, especially for polymers and viscoelastic materials. As temperature increases toward the glass transition temperature of a polymer, its Poisson's ratio tends to rise toward 0.5. For metals, the effect is generally small over normal engineering temperature ranges.
You need either (a) the transverse strain and axial strain of the material under load, or (b) the material's Young's modulus (E) and shear modulus (G). Strain values can be obtained from extensometers or strain gauges during a tensile test, while modulus values are often found in material datasheets.
Poisson's ratio is essential in structural analysis, finite element modeling, and material selection. It appears in stress-strain relationships, beam deflection formulas, and contact mechanics. Accurate knowledge of ν is required whenever multi-axial stress states are analyzed, such as in pressure vessels, bridges, and aerospace components.