# Wheatstone Bridge Calculator

URL: https://speedycalculator.com/calculators/physics/wheatstone-bridge/
Last updated: 2026-10-30

> The Wheatstone bridge calculator finds the unknown resistance of a balanced bridge, or the output voltage of an unbalanced bridge from its four resistances and supply voltage.

## Inputs

- Calculate
- R₁ (Ω, kΩ, MΩ, mΩ)
- R₂ (Ω, kΩ, MΩ, mΩ)
- R₃ (Ω, kΩ, MΩ, mΩ)
- R_x (Ω, kΩ, MΩ, mΩ)
- Supply voltage V_s (V, mV, kV, µV, MV)

## Results

- Unknown resistance R_x
- Bridge output voltage V_G

## Formula

```
Balanced: R_x = R₃·R₂/R₁ · Unbalanced: V_G = V_s·(R_x/(R₃ + R_x) − R₂/(R₁ + R₂))
```

## Explanation

The Wheatstone bridge measures resistance very precisely by comparing ratios rather than measuring current. Strain gauges, temperature sensors and load cells all use bridges.

### How to use the Wheatstone Bridge Calculator

- **Calculate**
- **R₁**
- **R₂**
- **R₃**
- **R_x**
- **Supply voltage V_s**

Results update as you type, every field has its own unit menu, and everything is calculated in your browser.

### How it works

Choose balanced (to find R_x) or unbalanced (to find the bridge voltage). R₁ and R₂ form one arm, R₃ and R_x the other.

### Inputs explained

FieldWhat to enterCalculateChoose one: Unknown resistance (balanced), Bridge output voltageR₁Units: Ω, kΩ, MΩ, mΩR₂Units: Ω, kΩ, MΩ, mΩR₃Units: Ω, kΩ, MΩ, mΩR_xUnits: Ω, kΩ, MΩ, mΩSupply voltage V_sUnits: V, mV, kV, µV, MV

### What each result means

- **Unknown resistance R_x** = [R₃]×[R₂]÷[R₁]
- **Bridge output voltage V_G** = [Supply voltage V_s]×([R_x]÷([R₃] + [R_x]) - [R₂]÷([R₁] + [R₂]))

### Example values

How the main result changes when **R₁** changes and everything else stays at the example values above:

R₁ (Ω)Unknown resistance R_x (Ω)0.560.754131.252.41.5221.5

## Worked example

Inputs — Calculate: Unknown resistance (balanced); R₁: 1 Ω; R₂: 2 Ω; R₃: 1.5 Ω.

Results — **Unknown resistance R_x = 3 Ω**.

## Key terms

- **Galvanometer**: Sensitive current detector.

## FAQ

**What does "balanced" mean?**
No current flows through the galvanometer; V_G = 0.

**Why is the bridge precise?**
It compares ratios, so supply variations cancel.

**Where are bridges used?**
Strain gauges, RTDs and load cells.

**What if V_G is negative?**
R_x is smaller than the balance value.


## Sources

- [OpenStax – University Physics Volume 2](https://openstax.org/details/books/university-physics-volume-2)
- [HyperPhysics (Georgia State University)](http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html)