True Strain Calculator

Written by Great Medico

Updated September 25, 2026 •2 min read

Share Print Save

The quickest way to trust a true strain estimate is to see how the answer responds when an input changes. Solid-mechanics results are only useful when the geometry, loading convention, and material property match the physical part being modeled. The sections below show what this page calculates, how it does it, and where the simplified model stops.

What this calculator does

The purpose of the True Strain Calculator is to evaluate true strain from Engineering strain (Ɛₑ), Engineering stress (σₑ). It is most useful for quick comparisons or hand-checks where the input definitions and displayed units remain part of the answer.

How to use it

Fill in the active quantities—Engineering strain (Ɛₑ), Engineering stress (σₑ)—and leave output-only boxes for the calculator to derive. Pay special attention to signs, angles, and whether a dimension is a radius, diameter, area, or length. Read the result together with its displayed unit.

How the calculation works

True strain is εtrue = ln(1+εeng). The page also converts engineering stress to true stress with σtrue = σeng(1+εeng), which is the uniform-deformation relation before necking becomes important.

Example

Using the default example on the page (Engineering strain (Ɛₑ) = 0.1; Engineering stress (σₑ) = 100 MPa), the calculator returns true strain of 0.09531. If a small input change sends the value in the opposite direction from the equation, recheck the selected unit and sign convention.

How to interpret the result

Treat the true strain as the value for the entered ideal geometry, loading state, and material constants. Compare it only with criteria that use the same stress, strain, hardness, or section-property definition and unit system.

Limitations and notes

Material properties can vary with alloy, processing, temperature, loading rate, direction, and test method; geometric idealizations also matter whenever the real part differs from the entered shape. An error in Engineering strain (Ɛₑ), Engineering stress (σₑ) can shift the answer far more than rounding does. The result is best used for estimation and comparison within the stated model; final engineering decisions should include the limits, factors, and checks required by the relevant standard.