Voltage Divider Calculator

You can use this voltage divider calculator to determine any one of the four variables associated with a simple two-resistor voltage divider when the values of the other three variables are available.

The four variables involved in a two-resistor voltage divider are input voltage (Vin), output voltage (Vout), resistance 1 (R1), and resistance 2 (R2).

The calculator also plots the circuit diagram and generates the component values.

How to use the voltage divider calculator:

  1. Input the three known variables
  2. Click on the "Calculate" button
  3. The calculator will display the remaining value and the circuit diagram.
Voltage Divider Calculator

Volts (V)

Volts (V)

Further Information

Engineers commonly use the two-resistor voltage divider circuit. The voltage divider, which is also frequently referred to as the potential divider, offers the distinct advantage that it can polarize the other elements in a circuit, including the integrated circuits and transistors, with a different voltage to that of the main voltage supply.

The main reason why this circuit is employed is to scale the input voltage down to a lower value according to the ratio of the two resistors.

This is achieved as follows:

  1. The ratio of the resistors (R1 and R2) reduces the input voltage to a lower output voltage.
  2. The output voltage represents a fraction of the input voltage. This fraction takes the form of R2 divided by the sum of R1 + R2.
  3. The basic formula used to determine the output voltage is based on Ohms Law and is as follows:

Vout = Vin * R2 / (R1 + R2)

For example, let's say we are working with a circuit that has a 12V input. However, one of the chips in the circuit needs 9 volts, while the other only needs 3 volts. A voltage divider can be used to distribute the voltage to the different chips according to their requirements.

If one resistor has a value of 2KΩ and the other has a value of 6KΩ, the 12-volt input will be divided into 3V and 9V.

Please note: You should never use a voltage divider for high voltages because the entire current will pass through the resistors, and this can cause damage. In this case, a better option would be a voltage regulator.

An Example:

Let's say we would like to determine the output voltage if the resistance of resistor R1 is 5KΩ, the resistance of resistor R2 is 10KΩ, and the input voltage is 9V.


Vout = Vin * R2 / (R1 + R2) = (9V) (10KΩ) / (5KΩ + 10KΩ) = 6V

Vout = 6 Volts.


This voltage divider calculator employs the following formulas:

Vout = Vin * R2 / (R1 + R2)

Vin = Vout * (R1 + R2) / R2

R1 = R2 * (Vin - Vout) / Vout

R2 = R1 * Vout / (Vin – Vout)

Where, Vout = output voltage (volts), Vin = input voltage (volts), R1 and R2 = resistor values (ohms).

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