Question 1

What is a voltage divider?

Accepted Answer

A voltage divider is a simple circuit made of two resistors in series that produces an output voltage that is a fraction of its input voltage. The output is taken across one of the resistors.

Question 2

What is the voltage divider formula?

Accepted Answer

Vout = Vin x R2 / (R1 + R2), where Vin is the input voltage, R1 is the top resistor (connected to Vin), and R2 is the bottom resistor (connected to ground). Vout is measured across R2.

Question 3

Can this calculator find R1 or R2?

Accepted Answer

Yes. Leave any one value (Vin, Vout, R1 or R2) blank and fill in the other three. The calculator solves for the missing value automatically.

Question 4

Why is the actual output voltage lower than calculated?

Accepted Answer

The formula assumes no load. When you connect a real circuit to Vout, it draws current and pulls the voltage down. To minimize this effect, choose resistor values so the divider current is at least 10x the load current.