Electronics
Wheatstone Bridge Calculator
Solve a four-resistor bridge two ways: find an unknown resistor when the bridge is balanced, or find the output voltage of an unbalanced bridge given all four resistors and an excitation voltage.
Solve for an unknown resistor at balance, or find the output voltage of an unbalanced bridge.
Bridge balance and output
Balance: R4 = R2·R3 / R1 Output: Vout = Vex·(R2/(R1+R2) − R4/(R3+R4))
A bridge is balanced (zero output) exactly when R1·R4 equals R2·R3. Strain gauges and precision resistance measurement both rely on detecting how far a bridge sits from that balance point.
How to use
- Choose whether you know three resistors and want the fourth, or you know all four and want the output voltage.
- Enter the known resistor values in ohms.
- For the output-voltage mode, also enter the excitation (supply) voltage across the bridge.
Example
Input: R1 = 100Ω, R2 = 220Ω, R3 = 100Ω, solving for R4 at balance
Output: R4 = 220 Ω
Student-friendly breakdown
This walkthrough emphasizes the most searched ideas for Wheatstone Bridge Calculator: wheatstone bridge calculator, bridge circuit calculator, unknown resistance calculator bridge. Start with the formula above, then follow the guided steps to double-check your work. For quick revision, highlight the givens, plug into the equation, and finish by verifying your units.
Need more support? Use the links below to open the long-form guide, browse additional examples, or hop into adjacent calculators within the same topic — each one is a quick way to double-check your work or handle a related question without starting from scratch.
Deep dive & study plan
Wheatstone Bridge Calculator: Solves for an unknown resistor at balance or the output voltage of a resistor bridge. It's built around wheatstone bridge calculator, bridge circuit, unknown resistance, so you can go from a raw question to a checked answer without switching tools.
The math behind it: A bridge is balanced (zero output) exactly when R1·R4 equals R2·R3. Strain gauges and precision resistance measurement both rely on detecting how far a bridge sits from that balance point. The core relationship is Balance: R4 = R2·R3 / R1 Output: Vout = Vex·(R2/(R1+R2) − R4/(R3+R4)), shown above the calculator so you can see exactly how your inputs turn into the result.
To use it well: (1) Choose whether you know three resistors and want the fourth, or you know all four and want the output voltage. (2) Enter the known resistor values in ohms. (3) For the output-voltage mode, also enter the excitation (supply) voltage across the bridge. Keep your units consistent as you go, and re-run a case you already know the answer to — it's the fastest way to catch a typo before it throws off a result you're relying on.
Worked example: entering R1 = 100Ω, R2 = 220Ω, R3 = 100Ω, solving for R4 at balance returns R4 = 220 Ω. Try swapping in your own numbers next, especially a case you're unsure about, before you use this for something that matters.
Quick retention checklist
- Speak the formula aloud (or annotate it) so the relationships stick.
- Write each step in your own words and compare with the numbered list above.
- Swap in new numbers for the Example to make sure the calculator (and your logic) handles edge cases.
- Check at least one related calculator below — it's the fastest way to confirm your numbers still line up from a different angle.
FAQ & notes
Where are Wheatstone bridges actually used?
Strain gauges, load cells, and RTD temperature sensors all use bridge circuits — a small resistance change from strain or temperature shows up as a measurable voltage the bridge equation converts back into that changing value.
What does a negative output voltage mean?
It just means the bridge is unbalanced in the opposite direction — R4's branch is pulling more of the excitation voltage than R2's branch. The sign shows direction, not an error.
What formula does the Wheatstone Bridge Calculator use?
A bridge is balanced (zero output) exactly when R1·R4 equals R2·R3. Strain gauges and precision resistance measurement both rely on detecting how far a bridge sits from that balance point.
How do I use the Wheatstone Bridge Calculator?
Choose whether you know three resistors and want the fourth, or you know all four and want the output voltage. Enter the known resistor values in ohms. For the output-voltage mode, also enter the excitation (supply) voltage across the bridge.