Voltage Divider Calculator

Voltage divider calculator is used to calculate the divided voltage across the series resistors.


Basic theory of Series Circuits

A series circuit contains two or more elements that are joined in the series configuration. Such circuits have two basic properties.

  1. Current always remains same through all components.
  2. Voltage always divides based on the magnitude of components. The higher the resistance, the higher is the voltage drop across it.

Let’s analyze a series circuit based on these two properties. Consider a circuit having a 10 V source which powers two series resistors of 5 Ω and 10 Ω.voltage-divider-circuitWe can easily apply the Ohm’s law for finding the current in the circuit.

Let’s first solve the series resistors:
Req = R+ R2 = 5 Ω + 10 Ω = 15 Ω

I = Vin / Req = 10 V / 15 Ω = 0.66 A

The equation in the previous line provides the current flowing through the circuit. The next step of our analysis is focused on divided voltage. We can apply the statement V = IR to 5 and 10 Ω resistors for calculating the individual voltage dropped across them. However, this step is tedious, probably in cases where we are not concerned with the current. An alternative solution is to use the voltage divider formula which is a simple equation.

Voltage divider formula and circuit

The circuit below is a voltage divider circuit with two series resistors along with the basic voltage divider formula.


We can apply the same formula to calculate the potential of the first resistor.


We can redraw the above circuit in an alternate form:


For a general case, the circuit and formula become:


Examples of Voltage Divider Rule

Example 1: A VDR circuit contains two series resistors of 5 kΩ and 10 kΩ. The input source provides 10 volts to the circuit. Find the voltage across both resistors.

Solution: V1 = [R1 / {R1 + R2} ] * Vin

= [ 5 kΩ / { 15 kΩ} ] * 10 V

= 3.33 volts