Elongation Calculator

What Is Elongation?

Elongation describes how much a specimen stretches under tension. Engineers use axial extension, engineering stress, and strain to check whether a part stays within elastic limits.

Elongation and Strain Formulas

Axial elongation under force $F$ on a bar with length $L$, area $A$, and Young modulus $E$:

$$\delta = \frac{FL}{AE}$$

Engineering stress and strain:

$$\sigma = \frac{F}{A}, \quad \epsilon = \frac{\sigma}{E} = \frac{\delta}{L}$$

Percent elongation from measured lengths:

$$E_p = \frac{L_f - L_o}{L_o} \times 100\%$$

Example: 50 kN on a 2 m bar with 1000 mm² area and 200 GPa modulus stretches about 0.5 mm with stress near 50 MPa.

Frequently Asked Questions

What is the difference between elongation and strain?

Elongation is the absolute length change. Strain is the fractional change, often shown as a percent of original length.

Why does a larger cross-section reduce elongation?

Stress is force divided by area. A larger area lowers stress and therefore lowers strain for the same force.

What is Young modulus?

Young modulus is stiffness in tension or compression. Higher modulus means less elongation for the same stress.

When does Hooke's law apply?

Stress stays proportional to strain only in the elastic region. Beyond yield, permanent deformation begins.

Can elongation be negative?

Yes under compression the final length is shorter, giving negative elongation or compressive strain.

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What Is Elongation?

Elongation and Strain Formulas

Frequently Asked Questions

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