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Strain calculator
Materials
Strain is the extension divided by the original length. It has no unit.
ε = Δx / x
This free calculator is for A-level physics. Choose the quantity you want to find, enter the other values with their units, and it shows the working in the layout used in exams, with the answer to the number of significant figures you choose. The values shown are an example. Change them to your own.
Quantity to find
Working
- Write the equationε = Δx / x
- Substitute the valuesε = 0.0012 ÷ 2
- Calculateε = 6 × 10−4
- Give the answer to 3 significant figuresε = 6.00 × 10−4
Worked example
Find ε, the strain. Given: extension Δx = 0.00120 m; original length x = 2.00 m.
- Write the equationε = Δx / x
- Substitute the valuesε = 0.0012 ÷ 2
- Calculateε = 6 × 10−4
- Give the answer to 3 significant figuresε = 6.00 × 10−4
Symbols and units
| Symbol | Quantity | SI unit |
|---|---|---|
| ε | Strain | no unit |
| Δx | Extension | m |
| x | Original length | m |
Strain: rearranged
- To find strain: ε = Δx / x
- To find extension: Δx = ε x
- To find original length: x = Δx / ε
Exam tip
Use the original length, not the stretched length. Both lengths in the same unit.
Common questions
What is the formula for strain?
The equation is ε = Δx / x, where ε is the strain; Δx is the extension (m); x is the original length (m).
What units should I use for strain?
In SI units: strain in no unit (a ratio), extension in m, original length in m. The calculator also accepts common alternatives such as kilometres, grams or minutes, and converts them for you.
How do I rearrange ε = Δx / x?
Rearranging gives these forms: to find strain: ε = Δx / x. to find extension: Δx = ε x. to find original length: x = Δx / ε.
Practise strain questions
Press the button for a question with random numbers. Work it out on paper first, then type your answer.
Related
More materials equations: Stress, Young modulus. See the full list on the a-level physics equation calculator page.