Wheatstone Bridge Calculator

This calculator is designed to help calculate missing resistor values (R4) for balanced bridges (Vb = 0). The calculator can also provide you with the voltage across the bridge (Vb), if you provide the resistor values (R1, R2, R3, R4), and input voltage (Vin).

How to use the calculator

  • Decide on your calculation parameters:
  • 1. Calculate R4 resistance for a balanced bridge, or
  • 2. Calculate the cross-bridge voltage Vb.
  • To calculate R4, select "Resistance of R4 for balanced bridge" and add the values for R1, R2, and R3 as directed.
  • To calculate the cross-bridge voltage, select "Voltage across the bridge Vb" and input the values for R1, R2, R3, R4, and Vin (input voltage) as directed.
  • Clicking the "Calculate" button will provide you with your results.
Wheatstone Bridge Calculator


Wheatstone bridges are tools used to ascertain electrical resistance via comparison. They are essentially electrical circuits that measure resistance when the capacity of a resistor is not known by passing an electrical current through it.

Wheatstone bridges comprise a pair of potential dividers, one of which employs the resistors R1 and R2, and the other of which employs the resistors R3 and R4. The bridge voltage is measured at the midpoint of the two voltage dividers. The bridge may be classified as balanced when the voltage between R1 and R2 equals the voltage between R3 and R4. The bridge voltage will equate to 0 at this point, with R1/R2 = R3/R4.

If the bridge is balanced, the current will be zero as well. If we know the bridge is balanced, we can discover the value of R4 with the formula:
R4 = R3 * R2 / R1

If we know the values for all four resistors as well as the supply voltage, then we can calculate the cross-bridge voltage through ascertaining the voltage for each potential divider and then subtracting one from the other, thus:

Vb = (R4 / (R3 + R4) * Vin) - (R2 / (R1 + R2) * Vin)

Vb = (R4 / (R3 + R4)) - (R2 / (R1 + R2)) * Vin

Wheatstone bridges are frequently employed to measure small levels of resistance, which makes them useful for such applications as resistance thermometers and strain gauges. Generally employed in electrical measurement circuits, Wheatstone bridges are an essential element of low-temperature alarms. Using different forms of Wheatstone bridge, it is possible to measure impedance, inductance, and capacitance.

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