Engineering Strain Calculator
Calculate signed engineering strain, percent strain and microstrain from an original length and length change, with independent metric and US units.
Measure relative extension or shortening from an original gauge length and its change. Engineering strain compares the change with the original length, so it has no physical unit. This calculator reports the same ratio as a decimal, a percentage and microstrain, with separate units for the two length inputs.
How to use this tool
- Enter the original positive gauge length.
- Select its unit, such as metres or inches.
- Enter a signed length change and its own unit, such as millimetres.
- Read the strain representations and check the resulting final length.
Formula
ε = ΔL / L₀; percent strain = 100ε; microstrain = 1,000,000ε
L₀ is the original gauge length and ΔL is final length minus original length. Both are converted to metres before division. Positive strain means extension; negative strain means shortening under the convention used here.
Example
A wire initially 2 m long extends by 1 mm, or 0.001 m. Its engineering strain is 0.001 / 2 = 0.0005, equivalent to 0.05% or 500 µε. Its final length is 2.001 m.
Frequently asked questions
Is strain the same as displacement?
Displacement or extension has a length unit. Strain divides that extension by a reference length, allowing specimens of different lengths to be compared on a relative basis.
What is microstrain?
One microstrain is one millionth of a dimensionless strain. It is a convenient scale for small deformations; it is not a different material property.
Is this true strain?
No. Logarithmic true strain for a uniform axial length change is ln(L/L₀). Engineering and logarithmic strain are close for very small changes but diverge as deformation grows.
Can the calculation be used outside the elastic range?
The geometric engineering ratio can still be computed, provided final length stays positive. Interpreting it as elastic strain requires other evidence. It does not include bending strains, shear strains, a strain tensor or a material failure assessment.
Sources
Last updated: 2026-10-30