Calculator Inputs
Use original and final length, or original length and extension. Optional force and area fields add stress and secant modulus outputs.
Formula Used
% Elongation = ((Final Length − Original Length) ÷ Original Length) × 100
Engineering Strain = (Final Length − Original Length) ÷ Original Length
True Strain = ln(Final Length ÷ Original Length)
Engineering Stress = Applied Force ÷ Original Area
Secant Modulus = Engineering Stress ÷ Engineering Strain
Percent elongation is a common tensile-test output for assessing ductility. It compares the permanent or observed increase in gauge length against the starting gauge length.
How to Use This Calculator
- Enter a specimen name and test ID if you want labeled output.
- Select the calculation mode.
- Type the original gauge length.
- Enter either final length or extension, based on the selected mode.
- Choose the length unit.
- Optionally enter original area and applied force for stress-related results.
- Select decimal precision.
- Press the calculate button to show the results above the form.
- Use the CSV and PDF buttons to save the output.
Example Data Table
| Sample | Original Length (mm) | Final Length (mm) | Extension (mm) | Percent Elongation (%) |
|---|---|---|---|---|
| A | 50.00 | 62.50 | 12.50 | 25.00 |
| B | 80.00 | 88.00 | 8.00 | 10.00 |
| C | 25.00 | 26.75 | 1.75 | 7.00 |
| D | 100.00 | 135.00 | 35.00 | 35.00 |
Frequently Asked Questions
1. What does percent elongation measure?
It measures how much a specimen lengthened during tensile loading compared with its original gauge length. Higher values usually mean better ductility.
2. Why is gauge length important?
Gauge length sets the reference distance for the strain calculation. Using the wrong starting length produces an incorrect elongation percentage.
3. What is the difference between engineering strain and true strain?
Engineering strain uses the original length as the reference. True strain uses the continuously changing length and better represents larger deformations.
4. Can final length be smaller than original length?
Not for a normal elongation result. A smaller final length would indicate compression, shrinkage, bad data entry, or an incorrect measurement basis.
5. Do units change the answer?
No. Percent elongation is dimensionless. Units only matter for consistent input conversion before the ratio is calculated.
6. Why include force and area fields?
They let the page estimate engineering stress and secant modulus. Those extra outputs help connect stretching behavior with loading conditions.
7. What percent elongation indicates good ductility?
That depends on the material and test standard. In general, higher elongation means greater ductility, while very low values suggest brittle behavior.
8. Where is this calculator useful?
It is useful in material testing, mechanical labs, classroom demonstrations, quality checks, and tensile report preparation.