Calculator input
Use decimal strain values. For example, 1% strain should be entered as 0.01. Moduli must use the same unit system.
Formula used
Direct strain relation
ν = -εlateral / εaxial
This is the standard definition. It compares lateral contraction with axial extension or compression.
From Young’s and shear modulus
ν = E / (2G) - 1
Use this when elastic testing provides Young’s modulus and shear modulus in the same unit system.
From bulk and shear modulus
ν = (3K - 2G) / (2(3K + G))
This relation is useful for isotropic materials when volumetric stiffness and shear resistance are known.
How to use this calculator
- Choose the input method that matches your available test data.
- Enter the material name and sample ID for clearer exports.
- For strain mode, enter axial and lateral strains as decimals, not percentages.
- For modulus modes, keep all modulus values in the same unit.
- Click the calculate button to show the result above the form.
- Use the chart and downloads to review trends and save the calculation.
Example data table
| Material | Typical Poisson ratio | Behavior note |
|---|---|---|
| Steel | 0.30 | Common structural metal with moderate lateral contraction. |
| Aluminum | 0.33 | Light metal with slightly higher lateral deformation than steel. |
| Concrete | 0.20 | Lower lateral response than many ductile metals. |
| Glass | 0.22 | Brittle material with modest transverse contraction. |
| Cork | 0.00 | Very little lateral expansion or contraction during compression. |
| Rubber | 0.49 | Nearly incompressible response under loading. |
Frequently asked questions
1. What is Poisson ratio?
Poisson ratio measures how much a material contracts or expands sideways when stretched or compressed along another direction. It is a dimensionless property.
2. Why is there a minus sign in the formula?
Axial tension usually causes negative lateral strain. The minus sign makes the reported Poisson ratio positive for ordinary materials that narrow when stretched.
3. Is Poisson ratio always positive?
No. Some engineered or cellular materials are auxetic and can have negative Poisson ratios. They expand laterally when stretched instead of narrowing.
4. What values are common for real materials?
Many metals fall near 0.25 to 0.35. Rubber-like materials approach 0.5, while cork is close to zero. Auxetic materials can be negative.
5. What does a value near 0.5 mean?
A value near 0.5 indicates nearly incompressible behavior. The material changes shape easily but resists volume change during elastic deformation.
6. What does a negative Poisson ratio mean?
A negative value means the material expands sideways during tension or narrows during compression. This unusual behavior is called auxetic response.
7. Can I calculate Poisson ratio from elastic constants?
Yes. This page supports both E with G and K with G. All modulus values must use the same unit system.
8. Do modulus units affect the ratio?
The ratio itself is dimensionless, but the modulus formulas require consistent units. Mixing MPa and GPa without conversion will give wrong results.