Voltage Divider Calculator

Calculate loaded or unloaded resistor-divider output voltage, current and power

Your result will appear here.

About the Voltage Divider Calculator

Voltage Divider Calculator finds the output voltage produced by two or more resistors connected in series across a supply. It is a common electronics calculation for reference voltages, sensor scaling and bias networks.

The ideal divider relationship assumes the output is not significantly loaded. A connected device with finite input resistance can change the effective lower resistance and reduce the actual output voltage.

How to Use the Voltage Divider Calculator

  1. Enter the supply voltage.
  2. Enter the resistor values in the divider.
  3. Choose the output node or resistor across which voltage is measured.
  4. Calculate the ideal output and consider load resistance separately when the connected circuit is not high impedance.

How the Calculation Works

For a two-resistor divider with R1 above the output node and R2 below it, Vout = Vin × R2/(R1+R2).

This follows from the series current I = Vin/(R1+R2) and Vout = I×R2. If a load is connected across R2, R2 should be replaced by the parallel equivalent of R2 and the load for a loaded-divider estimate.

Worked example

Voltage Divider Calculator Worked Example

12 V with R1=3 kΩ and R2=1 kΩ

Vout = 12×1/(3+1) = 3 V in the ideal unloaded divider.

Result guide

Understanding Your Voltage Divider Calculator Result

The result is the ideal node voltage for the entered resistor network. It does not guarantee that the divider can supply useful current to a low-resistance load.

Before you rely on the answer

Assumptions and Limitations

  • Resistors are connected in the intended series-divider arrangement.
  • Input supply is stable for the modeled condition.
  • Load current is negligible unless load resistance is explicitly included.

Practical tip

Using This Result in Practice

For analog-to-digital inputs or sensor interfaces, compare divider output impedance with the receiving circuit’s input requirement. A divider that produces the right no-load voltage can still perform poorly when loaded.

Related calculations

Useful Calculations to Continue With

If a load resistance must be combined with the lower divider resistor, use the Parallel Resistance Calculator.

Ohm's Law Calculator — If you need the divider current as well as voltage, use the Ohm’s Law Calculator.

Common questions

Voltage Divider Calculator FAQ

What is the basic voltage divider formula?

For two series resistors, Vout=Vin×R2/(R1+R2) when output is measured across R2.

Why does a connected load change divider voltage?

The load sits in parallel with part of the divider, changing the effective resistance ratio.

Can a voltage divider power a large load?

Usually it is intended for low-current signal or reference use; substantial loads require a suitable power circuit.