Stress & Strain Calculator
A free, browser-based calculator. Runs entirely in your browser — no sign up, nothing stored.
Enter Values
How to use this calculator
- Enter the axial force F (kN) and the cross-sectional area A (mm²).
- Optionally add the original length and the extension to also get strain.
- Read the axial stress, and (if lengths given) the strain and implied modulus.
How it works
The Stress & Strain Calculator gives the direct (axial) stress σ = F / A — and, if you supply the original length L₀ and extension ΔL, the strain ε = ΔL / L₀.
Because 1 N/mm² equals 1 MPa, a force in newtons over an area in mm² gives stress directly in MPa. Strain is dimensionless; multiplied by 100 it's a percentage. With both, the slope σ/ε is the implied Young's modulus.
Worked example
50 kN over 200 mm², stretching 1.25 mm in 1 m. σ = 50,000 / 200 = 250 MPa; ε = 1.25 / 1000 = 0.00125 (0.125%); implied E = 250 / 0.00125 = 200 GPa (steel).
Tips
- Stress and strain are only proportional in the elastic region — past yield the relationship curves.
- For a bar, A = π·d²/4; for a rectangle, A = width × thickness.
Frequently asked questions
Is the area the original or the necked area?
This computes engineering stress, which uses the original cross-sectional area. True stress uses the instantaneous (necked) area and is larger near failure.
Can I use these results for final design?
No. These calculators are for first-pass sizing, checking and learning. They assume ideal supports, static loads and elastic behaviour, and they don't apply load factors, member capacity, buckling or connection checks. Always verify against the relevant design code (e.g. AS 4100, AS 1170, Eurocode) and have a qualified engineer sign off structural work.
Related tools
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.