Voltage Divider Calculator
Output voltage = input × R₂ ÷ (R₁ + R₂)
Find the unloaded output of a two-resistor voltage divider.
Formula
Output voltage = input × R₂ ÷ (R₁ + R₂)
Worked example
Input voltage: 12 V
Upper resistance: 1000 Ω
Lower resistance: 2000 Ω
With these inputs, the result is 8 V.
How to use this calculator
- Identify the quantity you want to calculate.
- Enter your measurements in the units shown on each field.
- Read the result, which updates as you change the inputs.
- Check the assumptions below before applying the result.
Assumptions and limits
Load resistance is excluded and can materially change the real output.
Precision and checking
Results are rounded for display. Use the most accurate measurements available, and avoid rounding your inputs unnecessarily. Extra decimal places in a result do not make an estimate more reliable.
To check a result, substitute the same input values into the formula shown above. Change one value at a time to understand how the quantity responds.
Frequently asked questions
What assumptions does this calculation use?
Load resistance is excluded and can materially change the real output.
Are my inputs sent to a server?
No. The calculation runs locally in your browser. The result updates as you edit the inputs.
Sources & references
- NIST Guide to the SI — National Institute of Standards and Technology
