Voltage Divider Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: July 27, 2026How a voltage divider works
- Connect two resistors (R1 and R2) in series across the input voltage source.
- R1 sits on the high side, connected to the input voltage.
- R2 sits on the low side, connected to ground.
- The output voltage is measured at the junction between R1 and R2.
Worked example
For a 12V input with R1 = 1000 ohms and R2 = 2000 ohms:
Vout = Vin x (R2 / (R1 + R2)) = 12V x (2000 / 3000) = 8.0 V
Voltage dividers are the go-to method for scaling a higher voltage signal down to a safe range for a microcontroller input, or for creating a reference voltage from a single supply rail. Keep in mind this simple formula assumes negligible current is drawn from the output point - if a load pulls significant current from Vout, the actual output voltage will sag below this calculated value.