Strain Gauge Calculator
This strain gauge calculator works out the mechanical strain a gauge is experiencing from the resistance change it produces, turning a tiny electrical signal into a meaningful engineering number. A strain gauge is a resistor bonded to a surface that stretches or compresses with it, so its resistance shifts slightly whenever the surface deforms; the gauge factor tells you how sensitive that particular gauge is. Enter the resistance change (delta R) in ohms, the gauge's nominal resistance in ohms, and its gauge factor, and the calculator divides the fractional resistance change by the gauge factor to return the strain. You get three results: the strain itself as a dimensionless ratio, the same figure converted to microstrain (strain multiplied by one million, the units most datasheets and instruments use), and the fractional resistance change (delta R over R) that produced it. This mirrors how load cells, pressure transducers and structural monitoring sensors are actually characterised, and matches the maths behind a Wheatstone bridge circuit, which is how tiny resistance changes are usually measured in practice. It is built for electronics students, hobbyists and engineers checking sensor readings or coursework by hand. The calculator assumes ideal components and ordinary metal foil gauge factors around 2; real-world results depend on your gauge's actual specifications, temperature effects and wiring, so treat the output as an indicative engineering estimate rather than a certified measurement.
The formula
Strain is the fractional resistance change divided by the gauge factor: strain = (delta R / R) / GF. Strain is dimensionless; microstrain is the strain times one million. The gauge factor is typically about 2 for metal foil gauges.
Worked example
A 120 ohm gauge with gauge factor 2 showing a 0.24 ohm rise has delta R / R = 0.002, so strain = 0.002 / 2 = 0.001, that is 1000 microstrain. Enter 0.24, 120, 2 to confirm.
Frequently asked questions
What is the gauge factor?
The ratio of fractional resistance change to strain. Metal foil gauges have a gauge factor of about 2.
What is microstrain?
Strain expressed in millionths. A strain of 0.001 is 1000 microstrain.
How is strain measured in practice?
Usually with a Wheatstone bridge, which turns the tiny resistance change into a measurable voltage.
Who this calculator is for
This calculator is for electronics students, hobbyists and engineers.
What this calculator assumes
- You enter values in the units shown.
- Ideal components are assumed.
- Results are rounded for display.
Formula and sources
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