Poisson's Ratio Calculator
Enter the axial strain and lateral strain observed in a tensile or compressive test to compute Poisson's ratio. Add Young's modulus to also get the bulk and shear moduli.
GPa
Dimensionless; −1 < ν < 0.5 for stable isotropic materials
- 1
Strain ratio ε_lateral ÷ ε_axial
-0.006 ÷ 0.02 = -0.3 - 2
Poisson's ratio ν = −(ε_lateral ÷ ε_axial)
−(-0.3) = 0.3000Negative sign: under tension the lateral dimension contracts - 3
Shear modulus G = E ÷ (2 × (1 + ν))
200 GPa ÷ (2 × (1 + 0.3)) = 76.9231 GPa
How does this calculator work?
Poisson's ratio ν = −ε_lateral / ε_axial is the dimensionless ratio of transverse to axial strain. Enter both strains to get ν instantly. Add Young's modulus E to also compute the bulk modulus K = E/[3(1−2ν)] and shear modulus G = E/[2(1+ν)]. Stable isotropic materials have −1 < ν < 0.5.
Formula
How this is calculated
Poisson's ratio (ν) describes how much a material contracts laterally when stretched axially — or bulges laterally when compressed. It is defined as the negative ratio of transverse to axial strain: ν = −ε_lateral / ε_axial. For most common structural materials (steel, aluminium, concrete, glass) ν falls between 0.2 and 0.35. A value of 0.5 means the material is incompressible (rubber approaches this), while negative values (auxetic materials) indicate the material expands laterally under tension.
When Young's modulus E is provided, the calculator derives the two other independent elastic constants for an isotropic material. The bulk modulus K = E / [3(1−2ν)] measures resistance to uniform compression; it approaches infinity as ν → 0.5. The shear modulus G = E / [2(1+ν)] measures resistance to shape change at constant volume.
All three constants assume linear elastic, isotropic, homogeneous behaviour — valid for small strains well below the material's yield point. Anisotropic materials (composites, wood, single crystals) require a full 4th-order elasticity tensor and cannot be fully described by these three scalars.
Frequently asked questions
Structural steel has ν ≈ 0.26–0.30. Most metals fall in the range 0.25–0.35. Rubber is close to 0.5 (nearly incompressible), while cork is close to 0 (no lateral deformation), and some engineered foam structures are auxetic (negative ν).
A Poisson ratio ≥ 0.5 would imply the bulk modulus K ≤ 0, meaning the material would expand under hydrostatic pressure — physically impossible for a stable solid. The lower bound −1 follows from requiring G > 0.
A standard tensile test mounts strain gauges both along and perpendicular to the loading axis. The ratio of the two gauge readings at any load below yield gives ν directly. Digital image correlation (DIC) can measure both components non-contact from full-field surface deformation images.
Also known as
TG we-Calculate Editorial Team. (2026). Poisson's Ratio Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/poissons-ratio-calculator
TG we-Calculate Editorial Team. "Poisson's Ratio Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/poissons-ratio-calculator.
TG we-Calculate Editorial Team, "Poisson's Ratio Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/poissons-ratio-calculator
@misc{wecalculate_poissons_ratio_calculator, title = {Poisson's Ratio Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/poissons-ratio-calculator}}, year = {2026}, note = {TG we-Calculate} }
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