Wheatstone Bridge Calculator

The Wheatstone bridge is a very useful circuit. When fully balanced (R1 = R3 and R2 = Rx), the voltage across the bridge is zero. A small change in any resistance unbalances the bridge and produces a voltage difference. Wheatstone bridges are used in strain gauges, pressure sensors, and many other transducers.

A differential amplifier can extract the differential signal while rejecting common-mode noise. Very small signal changes can be extracted from the bridge because common-mode noise is easily rejected.

Input parameters

V_in(input voltage)

Result

Rx (unknown resistance)

V_B(bridge voltage)

Wheatstone bridge circuit diagram

Formula

Bridge voltage calculation

V_B = V_in × [Rx/(R3+Rx) - R2/(R1+R2)]

Unknown resistance calculation

Rx = (R2×R3 + R3×(R1+R2)×(V_B/V_in)) / (R1 - (R1+R2)×(V_B/V_in))

Approximate formula (when R3 = R1, Rx = R2 + δ, and δ is much smaller than R1 + R2)

V_B ≈ V_in × δ/(R1+R2)

Thus the bridge voltage is approximately proportional to the error δ, divided by the resistance sum on one side.

How to use:
• Click "Calculate V_B →" to compute the bridge voltage from the known Rx
• Click "← Calculate Rx" to compute the unknown resistance Rx from the known bridge voltage V_B
• The two calculation directions can be used independently; input values can be edited manually