Strain Gauge Calculator

This strain gauge calculator converts the resistance change of a strain gauge into mechanical strain. Enter the change in resistance, the nominal gauge resistance and the gauge factor, and the calculator returns the strain and the microstrain. A strain gauge is a resistor whose resistance changes when it is stretched or compressed; the gauge factor links the fractional resistance change to the strain. Dividing the fractional change by the gauge factor gives the strain, a dimensionless ratio usually quoted in microstrain (millionths). Strain gauges are at the heart of load cells, pressure sensors and structural monitoring. The formula, a worked example and the assumptions are below.

Resistance change \u0394R (\u03A9)

Nominal resistance R (\u03A9)

Gauge factor GF

Microstrain

Fractional \u0394R/R

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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