Resistor Divider Calculator

This tool calculates the voltage drop across each resistor in a series network of two resistors.


  • Input Voltage Vin
  • R1 and R2 in milliOhm/Ohm/kiloOhm/megaOhm

Formula for Resistor Divider

Ohm’s law is used to calculate V1 and V2. The current flowing through each series resistor is the same. The voltage drop across each is given by the formulas:



The larger voltage drop will be across the larger resistor value. Conversely, the smaller voltage drop will be across the smaller resistor.

If you want to calculate the voltage drop across a single resistor set R2=0 and from the equations above, V1=Vin and V2=0 (which makes sense).

Example Calculation

With R1=1Ω, R2=4Ω, Vin=12V, the voltages

  • V1=2.4V
  • V2=9.6V

The sum of the two voltages = the input voltage. As a check you can see that 2.4+9.6= 12V

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