📏 Elongation Calculator
Calculate elongation, percent elongation, and strain
Original length before deformation
Length after deformation (should be ≥ initial length)
How to Use This Calculator
Enter Initial Length
Input the original length (L₀) of the material before any deformation. This is typically measured before applying load or stress. Use consistent units (mm, cm, m, or inches).
Enter Final Length
Input the final length (Lf) of the material after deformation. This is measured after applying load, stress, or during material testing. Use the same units as initial length.
Calculate and Review
Click "Calculate Elongation" to get three results: elongation (ΔL), percent elongation (%), and strain (ε). These values are essential for material characterization and engineering analysis.
Formula
ΔL = Lf - L₀
% Elongation = [(Lf - L₀) / L₀] × 100
Strain (ε) = (Lf - L₀) / L₀ = ΔL / L₀
where:
- ΔL = Elongation (absolute change in length)
- L₀ = Initial length
- Lf = Final length
- ε = Engineering strain (dimensionless)
Example 1: Tensile Test
Given: Initial length = 100 mm, Final length = 120 mm
Elongation: ΔL = 120 - 100 = 20 mm
Percent Elongation: % = [(120 - 100) / 100] × 100 = 20%
Strain: ε = (120 - 100) / 100 = 0.20 (or 20%)
Example 2: Material Testing
Given: Initial length = 50 mm, Final length = 55 mm
Elongation: ΔL = 55 - 50 = 5 mm
Percent Elongation: % = [(55 - 50) / 50] × 100 = 10%
Strain: ε = (55 - 50) / 50 = 0.10
Typical Percent Elongation Values:
- Steel (structural): 15-25%
- Aluminum: 10-30%
- Copper: 20-45%
- Rubber: 100-800%
- Glass: 0.1-0.5%
- Concrete: 0.1-0.3%
About Elongation Calculator
The elongation calculator determines how much a material stretches when subjected to tensile forces. Elongation is a critical property in materials science and engineering, indicating a material's ductility and ability to deform plastically before failure. It's measured in three ways: absolute elongation (ΔL), percent elongation (%), and engineering strain (ε).
When to Use This Calculator
- Material Testing: Calculate elongation from tensile test data
- Quality Control: Verify materials meet elongation specifications
- Engineering Design: Determine material ductility for design applications
- Research & Development: Characterize material properties for new materials
- Educational Purposes: Learn about material deformation and strain
Why Use Our Calculator?
- ✅ Complete Calculations: Calculates elongation, percent elongation, and strain
- ✅ Easy to Use: Simple interface requiring only two measurements
- ✅ Flexible Units: Works with any length units (mm, cm, m, inches)
- ✅ Formula Display: Shows all calculation formulas with step-by-step breakdown
- ✅ Free Tool: No cost, no registration required
- ✅ Mobile Friendly: Works on all devices
Common Applications
Tensile Testing: Materials engineers use elongation measurements to characterize material properties. Tensile tests pull specimens until failure, measuring how much they stretch. Percent elongation is a key indicator of material ductility.
Quality Control: Manufacturing industries measure elongation to ensure materials meet specifications. Materials that don't meet minimum elongation requirements may be too brittle for their intended use.
Material Selection: Engineers use elongation values to select appropriate materials. High elongation (ductile materials) are better for applications requiring deformation, while low elongation (brittle materials) may be better for stiffness-critical applications.
Failure Analysis: Elongation measurements help understand material failure modes. Materials with very low elongation may fail suddenly (brittle failure), while high elongation materials show warning signs before failure (ductile failure).
Tips for Best Results
- Use consistent units throughout (all metric or all imperial)
- For accurate results, measure initial length before applying any load
- Final length should be measured after deformation is complete
- For material testing, use standard test specimens with gauge lengths
- Remember that percent elongation depends on gauge length - longer gauge lengths typically give lower values
- For very large deformations, true strain may be more appropriate than engineering strain
Frequently Asked Questions
What is elongation?
Elongation is the increase in length that occurs when a material is subjected to tensile (stretching) forces. It can be expressed as absolute elongation (ΔL = Lf - L₀), percent elongation, or engineering strain. Higher elongation indicates more ductile (stretchable) material behavior.
What's the difference between elongation and strain?
Elongation (ΔL) is the absolute change in length (in units of length). Strain (ε) is the relative change, calculated as elongation divided by original length (dimensionless). Percent elongation is strain multiplied by 100. All three measure the same deformation, just in different forms.
What is a good percent elongation value?
Good elongation depends on the application. For structural steel, 15-25% is typical. For aluminum, 10-30% is common. Very ductile materials like rubber can have 100-800% elongation. Brittle materials like glass have very low elongation (less than 1%). Higher elongation generally means better ductility and resistance to sudden failure.
Does gauge length affect percent elongation?
Yes, percent elongation typically decreases as gauge length increases. This is because necking (localized thinning) occurs in a fixed region, so its effect is diluted over longer gauge lengths. For standardization, material specifications often specify the gauge length used (e.g., 50 mm or 2 inches).
Can elongation be negative?
For this calculator, elongation is positive (Lf ≥ L₀) because it's designed for tensile elongation. In compression, materials shorten (negative elongation), but we'd call that compression rather than elongation. For compressive deformation, you'd calculate percent reduction or compressive strain.
What is the difference between engineering strain and true strain?
Engineering strain (used here) is calculated as (Lf - L₀)/L₀ using original length. True strain is calculated as ln(Lf/L₀) using natural logarithm. For small deformations (less than 5%), they're nearly equal. For large deformations, true strain is more accurate because it accounts for the changing reference length during deformation.