By Zencalcy Editorial TeamLast reviewed About us
True stress accounts for the decreasing cross‑sectional area as a material necks during tensile testing. It is defined as the instantaneous load divided by the instantaneous area.
True stress from engineering stress and strain.
σₜ = σ (1 + ε)
σ is the engineering stress, ε the engineering strain. True stress continues to rise after engineering stress peaks during necking.
| Symbol | Meaning |
|---|---|
| σₜ | True stress. |
| σ | Engineering stress. |
| ε | Engineering strain. |
σₜ = σ (1 + ε) = 250 MPa × 1.2 = 300 MPa at 20 % strain.
Continue with the True Strain Calculator, Bearing Stress Calculator, or the Euler Buckling Calculator — or browse more materials and elasticity tools and all physics calculators.
When analysing necking, fracture, or forming processes where area reduction is significant.
Results are computed from the standard equations of classical mechanics. Unit conversions use the SI definitions published by NIST. Air resistance is ignored unless the calculator names a drag model.
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Last reviewed: September 2026. See how we build and check every tool on the about page.
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Content updated: September 2026