What is the Wheatstone bridge balance condition?

The bridge is balanced when R1/R2 = R3/Rx, which means Rx = R3 × R2 / R1. At balance, the voltage across the detector (output voltage) is exactly zero, so no current flows through it.

What are the units for resistance inputs?

Enter values in ohms (Ω). For example, enter 1000 for 1 kΩ or 1000000 for 1 MΩ. All four resistors must use the same base unit (ohms).

What is the bridge output voltage?

The output voltage Vout = Vs × (R3/(R1+R3) − Rx/(R2+Rx)) represents the potential difference between the two midpoints of the bridge. It is zero when the bridge is balanced.

Can I use this for strain gauge calculations?

Yes. Strain gauges are typically one arm of a Wheatstone bridge. Enter the nominal gauge resistance as Rx and the fixed resistors as R1, R2, R3 to find the output voltage at a given strain-induced resistance change.

What happens if R1 or (R2 + Rx) is zero?

Division by zero is undefined and the circuit would short. The calculator shows an error if any denominator is zero.

Wheatstone Bridge Calculator

Find the unknown resistance in a Wheatstone bridge, check balance, and see the bridge voltages for any supply voltage.

Bridge Resistances

All values in ohms (Ω). Rx is the unknown you want to find.

R1 (Ω) — top-left arm

R2 (Ω) — top-right arm

R3 (Ω) — bottom-left arm

Rx (Ω) — unknown (optional, for Vout check)

Supply Voltage Vs (V)

Balanced Rx (calculated)

—

Rx = R3 × R2 / R1

Balance Status

—

Bridge Output Voltage (Vout)

—

Vout = Vs × (R3/(R1+R3) − Rx/(R2+Rx))

Midpoint Voltages

Va (left midpoint)

—

Vb (right midpoint)

—

Key formulas

Balance condition: R1/R2 = R3/Rx

Unknown resistance: Rx = R3 × R2 / R1

Va (left): Vs × R3 / (R1 + R3)

Vb (right): Vs × Rx / (R2 + Rx)

Vout: Va − Vb

Summary

Find the unknown resistance in a Wheatstone bridge, check balance, and see the bridge voltages for any supply voltage.

How it works

Enter the three known resistances R1, R2, and R3 as numeric values in ohms.
Enter the supply voltage Vs applied across the bridge.
The calculator solves Rx = R3 × R2 / R1 using the Wheatstone balance equation.
It checks whether the actual Rx you entered matches the balanced value.
The bridge output voltage Vout = Vs × (R3/(R1+R3) − Rx/(R2+Rx)) is computed.
Click Calculate or press Enter after entering the values.

Use cases

Determine an unknown resistor value in a lab bridge circuit.
Verify that a strain gauge bridge is correctly balanced before measurement.
Design precision resistance measurement setups in electronics.
Check temperature sensor (RTD/thermistor) bridge calibration.
Troubleshoot sensor circuits that use bridge topology.
Educational exploration of Kirchhoff's voltage law in bridge networks.

Frequently Asked Questions

Last updated: 2026-09-22 · Reviewed by Nham Vu