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Wheatstone Bridge Calculator

Work out wheatstone bridge instantly with clear inputs, formula shown and shareable results.

About Wheatstone Bridge Calculator

A Wheatstone bridge balances when R1/R2 = R3/R4, so the unknown arm equals R2 x R3 / R1. Away from balance the output is the difference between two voltage dividers, which is why the bridge is the standard front end for strain gauges and resistance thermometers: it converts a tiny fractional resistance change into a differential voltage.

Formula

Wheatstone bridge

At balance R1 x R4 = R2 x R3, so Rx = R2 x R3 / R1

Worked example

With the default values below, Wheatstone Bridge Calculator returns Unknown resistance at balance of 1,000.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

R1
1,000 Ω
R2
1,000 Ω
R3
1,000 Ω
Excitation voltage
5 V

Results

Unknown resistance at balance
1,000.00 Ω
Bridge output with R4 = Rx + 1%
12.44 mV
Output per 1% change in Rx
12.44 mV/%
Bridge ratio R2/R1
1.0000

Step by step

  1. 1Values used
  2. 2Wheatstone bridge
  3. 3Unknown resistance at balance= 1,000.00 Ω
  4. 4Bridge output with R4 = Rx + 1%= 12.44 mV
  5. 5Output per 1% change in Rx= 12.44 mV/%
  6. 6Bridge ratio R2/R1= 1.0000

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.

Frequently Asked Questions

Why use a bridge rather than measure resistance directly?

The bridge output is zero at balance, so the small change of interest is measured against zero rather than as a tiny fraction of a large reading. That removes offset and gain error.

What limits sensitivity?

Excitation voltage, which is capped by self-heating of the sensing element, and the noise and drift of the instrumentation amplifier that follows.

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