Poisson ratio table
Poisson ratio for common materials. It describes how much a material thins sideways when stretched (or bulges when compressed): the ratio of lateral strain to axial strain. Most metals cluster near 0.3.
Poisson ratio (ν)
| Material | Poisson ratio |
|---|---|
| Steel | 0.30 |
| Stainless steel | 0.30 |
| Nickel | 0.31 |
| Cast iron | 0.26 |
| Aluminum | 0.33 |
| Copper | 0.34 |
| Brass | 0.34 |
| Bronze | 0.34 |
| Titanium | 0.34 |
| Magnesium | 0.35 |
| Lead | 0.44 |
| Glass | 0.22 |
| Concrete | 0.20 |
| Rubber | 0.49 |
| Cork | 0.00 |
Poisson ratio (v) is dimensionless and for most solids falls between 0 and 0.5. A value near 0.5, like rubber, means the material conserves volume and barely compresses. Near 0, like cork, it means stretching one way causes almost no sideways change, which is why cork pushes easily into a bottle.
Working a stress or torsion problem?
Poisson ratio links the elastic and shear moduli — see the Modulus of Elasticity and Shear Modulus tables.
What Poisson ratio means
Stretch a bar and it gets thinner; the Poisson ratio is how much thinner relative to how much longer. A ratio of 0.3 means a material narrows by three units sideways for every ten units it lengthens. It enters any calculation involving combined stresses, thick-walled pressure vessels, or the relationship between elastic and shear moduli.
The extremes: rubber and cork
Rubber has a ratio near 0.5, meaning it preserves volume: squeeze it one way and it bulges the others. Cork sits near zero, so it does not expand sideways when compressed, which is exactly why a cork can be pushed into a bottle neck while a rubber stopper resists. Most engineering metals live in the narrow band around 0.3.
FAQ
What is the Poisson ratio of steel?
About 0.30, like most metals. It means steel thins sideways by 0.3 units for each unit it stretches lengthwise.
Can the Poisson ratio be negative?
For ordinary materials no, but specially engineered auxetic structures can have a negative ratio, getting fatter when stretched. Common materials sit between 0 and 0.5.
Why is rubber close to 0.5?
A ratio of 0.5 means constant volume. Rubber barely changes volume under load, so stretching it one way makes it bulge equally in the other directions.