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Voltage divider calculator

Vout from two resistors, or the resistor for a wanted Vout.

Try the circuit in the labBuild it on the simulator's bench and measure it.

How it is worked out

Vout = Vin × R2 ÷ (R1 + R2). Two resistors in series share the voltage in proportion to their values.

Example: 12 V with R1 = 10 kΩ and R2 = 4.7 kΩ gives 12 × 4.7 ÷ 14.7 = 3.84 V.

A divider is for measuring (feeding an ADC pin, a comparator, a transistor base), not for powering anything: a load on the output pulls Vout down, because the divider's output resistance (R1 ∥ R2) is in series with it. Keep the load at least 10 times larger than R1 ∥ R2, or use a regulator.

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