Wheatstone Bridge Calculator
By Santaji GadepatilinUpdated October 27, 2026
A Wheatstone bridge measures very small resistance changes by balancing two voltage dividers against each other. It sits inside strain gauges, load cells, pressure sensors and RTD circuits — see these Wheatstone bridge applications.
How to use the Wheatstone bridge calculator
Enter the excitation voltage and the four resistances. The calculator gives the bridge output voltage (between the two midpoints) and the value of Rx that would balance the bridge.
Wheatstone bridge formulas
Vout = Vs × [Rx ÷ (R₃ + Rx) − R₂ ÷ (R₁ + R₂)]
Balance: Rx = R₃ × R₂ ÷ R₁
Example: 1% change in a quarter bridge
All arms 1,000 Ω, Rx = 1,010 Ω, 10 V excitation:
Vout = 10 × (1,010 ÷ 2,010 − 0.5) = 24.9 mV
Output vs resistance change (10 V, 1 kΩ arms)
| ΔR/R | Quarter bridge | Full bridge (4 active arms) |
|---|---|---|
| 0.01% | 0.25 mV | 1.0 mV |
| 0.1% | 2.50 mV | 10.0 mV |
| 0.5% | 12.47 mV | 50.0 mV |
| 1% | 24.88 mV | 100.0 mV |
| 2% | 49.50 mV | 200.0 mV |
| 5% | 121.95 mV | 500.0 mV |
Applications
- Strain gauges and load cells: tiny resistance changes from strain.
- RTD measurement: three-wire bridge circuits cancel lead resistance — see the Pt100 calculator.
- Pressure sensors: piezoresistive silicon bridges inside most pressure transmitters.
- Gas sensors and hot-wire anemometers.
Strain gauge output
For a quarter bridge, Vout ≈ Vs × GF × ε ÷ 4, where GF ≈ 2 for metal foil gauges. 1,000 µε at 10 V gives about 5 mV.
Frequently asked questions
What is the balance condition of a Wheatstone bridge?
The output is zero when R1 ÷ R2 = R3 ÷ Rx, so Rx = R3 × R2 ÷ R1.
How does a Wheatstone bridge measure small changes?
At balance the output is zero, so a small change in one resistor produces a small voltage that can be amplified, without a large fixed offset.
What is a quarter, half and full bridge?
The number of active sensing elements — one, two or four. A full bridge with four strain gauges gives four times the output of a quarter bridge and better temperature compensation.
Is the output linear?
Only approximately for small changes. For large changes, use the exact formula here.