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Voltage divider.

Calculate the output of a two-resistor voltage divider.

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10 V
5 V
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01 / QUESTION

With two equal series resistors and 10 V input, the unloaded output is:

Voltage splits equally: 10 × R ÷ (R + R) = 5 V.

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How the calculation works

Vout = Vin × R2 ÷ (R1 + R2). Branch current in mA equals Vin ÷ (R1 + R2) when R is in kΩ.

KEY FORMULAVout = Vin × R2 ÷ (R1 + R2). Branch current in mA equals Vin ÷ (R1 + R2) when R is in kΩ.
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Worked example

With 12 V, R1 = 10 kΩ and R2 = 5 kΩ, the output is 4 V and branch current is 0.8 mA.

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Before you rely on this result

The output is unloaded. Connecting a sensor or input can change the voltage; never exceed your microcontroller’s maximum input rating.

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Informational tool. It does not replace testing, measurement or professional advice when needed.

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Frequently asked questions

Can I wire the output to an ESP32?+

Only after verifying the actual voltage, pin input limits, tolerances and transients.

Which resistor unit should I use?+

Enter both values in kiloohms (kΩ).