# 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 very commonly employ 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 that is 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 full current has to pass 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.

### Solution:

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

Vout = 6 Volts.

## Formulas

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).

You may also be interested in our Resistor Color Code Calculator or Transformer Calculator