Elongation Calculator

Enter your specimen's original length, final length, and optionally material type to calculate elongation percentage and change in length. You can also switch to the axial force mode by providing load (P), cross-sectional area (A), and modulus of elasticity (E) to find deformation under tension. Results include percent elongation, absolute ΔL, and a breakdown chart — useful for material selection and structural design.

Select a material to auto-fill modulus of elasticity (axial mode).

mm

Length of the specimen before load is applied.

mm

Length of the specimen after load is applied.

N

Force applied along the axis of the member.

mm

Original length of the structural member.

mm²

Cross-sectional area perpendicular to the load.

MPa

Young's modulus of the material. Auto-filled when a preset material is selected.

Results

Elongation Percentage

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Change in Length (ΔL)

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Engineering Strain (ε)

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Axial Stress (σ)

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Failure Risk Indication

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Original Length vs Final Length (mm)

Frequently Asked Questions

What do you mean by elongation?

Elongation refers to the increase in length of a material specimen when subjected to a tensile (pulling) load. It is typically expressed as a percentage of the original length and is a key mechanical property used to assess a material's ductility — how much it can deform before fracturing.

How do I calculate elongation percentage?

Elongation percentage is calculated using the formula: Elongation (%) = ((Lf − Lo) / Lo) × 100, where Lo is the original (gauge) length and Lf is the final length after deformation. For example, if a 100 mm specimen stretches to 115 mm, the elongation is 15%.

What is elongation at break?

Elongation at break (also called fracture strain) is the elongation measured at the point when the material specimen ruptures or breaks during a tensile test. It indicates the maximum deformation a material can undergo before failure, and is a critical value in material selection for structural and flexible applications.

What is the elongation if the change in length is 5 mm for a 10 mm long object?

Using the elongation formula: Elongation (%) = (ΔL / Lo) × 100 = (5 / 10) × 100 = 50%. This means the object elongated by 50% of its original length.

What is the difference between elongation and strain?

Engineering strain (ε) is the dimensionless ratio of change in length to original length: ε = ΔL / Lo. Elongation percentage is simply this strain expressed as a percentage (ε × 100). Both measure the same deformation, just in different units.

How does modulus of elasticity relate to elongation?

The modulus of elasticity (Young's modulus, E) describes a material's stiffness — how much stress is needed to produce a given strain. A higher E means less elongation for the same applied load. The axial deformation formula is ΔL = (P × L) / (A × E), where P is load, L is length, and A is cross-sectional area.

Which materials have high elongation at break?

Highly ductile materials like Thermoplastic Polyurethane (TPU) and copper exhibit high elongation at break — sometimes exceeding 300–500%. Brittle materials like ceramics or some plastics (e.g., PLA) have very low elongation at break, often under 5%. Engineers choose materials based on whether flexibility or rigidity is needed.

Can elongation be negative?

Yes — if the final length is less than the original length, the result is negative elongation, which is called compression or shortening. The magnitude indicates the degree of compressive deformation. This calculator handles both tensile (positive) and compressive (negative) cases.

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