Stress and Strain Calculator
Enter the load and the area to get stress, and the extension and length to get strain. Add the modulus to find the elongation.
Typical values only. Use the figures from the material supplier for a real design.
Worked examples
Steel bar
10 kN on 100 mm2
100 MPa
10,000 / 0.0001.
Stretch
100 MPa on 2 m of steel (200 GPa)
1 mm
100e6 x 2 / 200e9.
About Stress and Strain Calculator
Stress is the load on a material divided by the area carrying it, measured in pascals. Strain is the fractional change in length, the extension divided by the original length, and has no unit. In the elastic range these are proportional to each other, and the ratio is Young's modulus, a property of the material. This is Hooke's law, and it holds until the material reaches its elastic limit.
Use the calculator to find the stress in a rod or cable, the strain from a measured stretch, or the modulus from a tensile test. If you give the stress and the modulus, it works out the extension. Enter the yield strength too, and you get how many times the stress is below yield, a useful margin check. A menu fills in typical moduli for steel, aluminium, copper, titanium and glass. The figures are for simple axial loading of a uniform bar, not for bending or buckling.
How to use Stress and Strain Calculator
- Enter the axial force and the cross-section area for stress.
- Enter the original length, and the change in length if measured, for strain.
- Enter or pick Young's modulus to find the extension, and the yield strength for a margin check.
- Read the stress, strain, modulus or extension.
Common uses
- Checking the stretch of a steel rod or wire under load
- Interpreting results from a tensile test
- Comparing materials by stiffness
- Engineering and materials science coursework
Frequently asked questions
What is the stress formula?
Stress = force / area. A 10 kilonewton load on 100 square millimetres gives 100 megapascals.
What is Young's modulus?
It is the stress divided by the strain in the elastic range, a measure of stiffness. Steel is about 200 gigapascals, aluminium 69 and copper 117.
How much will a bar stretch?
The extension is stress x original length / modulus. A 2 metre steel bar at 100 megapascals stretches 1 millimetre.
What happens above the yield strength?
The material deforms permanently and does not spring back. Designs keep working stress well below yield to leave a margin.