Calculate the true (logarithmic) strain for large deformations.
Input Parameters
Calculation Results
Enter lengths to calculate
About this calculator
Quick Reference
L₀Original gauge length
LInstantaneous length
ε_trueNatural or logarithmic strain
Overview
True strain (or logarithmic strain) is an alternative to engineering strain that is more accurate for large deformations because it accounts for the changing reference length as the material is stretched.
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Pro Tips
The formula is ε_true = ln(L / L₀).
For small deformations, true strain and engineering strain (ΔL / L₀) are almost identical.
True strain is additive: stretching 1m to 2m and then 2m to 3m has a total true strain that is the sum of the two steps.
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Fun Facts
"In tensile testing of ductile materials, 'necking' occurs when the specimen begins to thin locally, making true strain critical for accurate stress-strain curves."
"True strain can be greater than 1, whereas engineering strain is often expressed as a percentage."
"Rubbers and polymers can undergo massive true strains (often called 'stretch ratios') before failing."
