True Strain Calculator: Logarithmic Strain, True Stress and Multi-Pass Deformation

Your details

Choose which inputs you have. All modes calculate true strain; the stress mode also converts stress.
The gauge length before deformation.
mm
The gauge length after deformation (tensile: Lf > L0; compressive: Lf < L0).
mm
True strain (εₜ)Moderate plastic strain
0.1823

Logarithmic (true) strain - the main result for all modes

Engineering strain (εₑ)0.2
Elongation20%
True vs engineering strain difference0.0177
True strain0.1823
Engineering strain0.2

True strain is 0.1823 (tensile)

  • Engineering strain is 0.2000 and true strain is 0.1823, a difference of 0.0177 (8.8%). At small strains the two converge; at large strains the gap grows significantly.
  • Above 0.1, true strain is the correct measure for metal forming, finite element analysis, and flow stress calculations because it is additive across multiple deformation passes.

Next stepUse the true strain value with your material's strain-hardening exponent (n) and strength coefficient (K) to find the current flow stress: sigma_f = K * epsilon_t^n.

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