Calculate the output voltage of a resistive voltage divider from Vin, R₁ and R₂.
A voltage divider is two resistors in series across a voltage source. The output is taken across the second resistor and equals Vin × R₂ / (R₁ + R₂). It is the most common way to step down a voltage without a regulator — used in sensor interfaces, biasing and level shifting.
The formula assumes no load on the output. In practice, whatever you connect to Vout draws current through R₂ and changes the ratio. For a stiff divider, keep the load impedance at least ten times higher than R₂.
This calculator gives the unloaded Vout. For loaded dividers, add the load resistance in parallel with R₂ and recalculate.
Vout = Vin × R₂ / (R₁ + R₂).
The load resistance appears in parallel with R₂, lowering the effective R₂ and dropping Vout. Keep the load impedance at least 10× R₂ for the formula to hold.
Technically yes, but resistive dividers waste power as heat and provide no isolation. Use a transformer or a switching regulator for mains.
No. The calculation runs locally in JavaScript.
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