How is voltage-divider output calculated?

For an unloaded divider, output voltage equals input voltage multiplied by R2 divided by the sum of R1 and R2.

How does a load change a voltage divider?

A load from the output to ground is parallel with R2, reducing the effective lower resistance and usually lowering the output voltage.

Can this calculator solve for a resistor?

Yes. It can solve for R1 or R2 from input and target output voltage, then optionally select a preferred E-series value and show the actual resulting output.

Voltage Divider Calculator

Explore an ideal or loaded two-resistor divider, solve for voltage or resistance, and see current, power, and output impedance instantly.

Voltage Divider Calculator

Explore an ideal or loaded two-resistor divider, solve for voltage or resistance, and see current, power, and output impedance instantly.

Live circuit preview

Two-resistor divider

Output voltage

2.5 VIdeal · no load

5 V through 10 kΩ and 10 kΩ

Divider current: 250 µA
R1 power: 625 µW
R2 power: 625 µW
Output resistance: 5 kΩ

Formula guide

How a voltage divider works

Unloaded output

V_out = V_in × R2 ÷ (R1 + R2)

With a load

R_lower = R2 ∥ RL, then use it as the lower divider resistance.

Output resistance

R_th = R1 ∥ R2, the divider’s Thevenin resistance.

Voltage dividers are useful for reference and signal voltages under light loads. They are generally not substitutes for regulated supplies when powering significant or changing loads.

Voltage Divider Calculator

Two-resistor divider

Ideal versus loaded output

How a voltage divider works