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Voltage Divider

Also known as potential divider

Vout=VinR2R1+R2V_{out} = V_{in} \frac{R_{2}}{R_{1} + R_{2}}
sig figs

Worked example: 12 V over 10 kΩ + 5 kΩ → 4 V. Press Try an example to run it live, then adjust anything.

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Where Voltage Divider fits

Your answer feeds
Decibel Voltage Gain

See also

Decibel Voltage Gain: Both use output voltage and input voltage.555 Astable Frequency: Both use upper resistance.Current Divider: Both use upper resistance.LED Series Resistor: Both use upper resistance.Q Factor of a Series Resonant Circuit: Both use upper resistance.Series RL or RC Impedance: Both use upper resistance.
3 more relatedSeries RLC Impedance: Both use upper resistance.RC Cutoff Frequency: Both use upper resistance.RL Cutoff Frequency: Both use upper resistance.
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Voltage Divider explained

R₁R₂VinVout

Series resistors carry the same current, so each takes a share of the voltage in proportion to its resistance: the divider is Ohm's law applied twice. Twelve volts across 10 kΩ over 5 kΩ puts 12 × 5/15 = 4 V at the junction. It is the most-used circuit in electronics: bias networks, level shifters, the feedback string that sets a regulator's output, and every potentiometer, which is just a divider with a movable tap.

The trap is loading. This formula assumes nothing draws current from the tap; connect a load comparable to R₂ and the output sags, because the load parallels R₂. The rule of thumb is to make the divider current at least ten times the load current, but not so low-resistance that it wastes power. That trade-off is why high-impedance dividers pair with op-amp buffers, and why measuring a 1 MΩ divider with a cheap 1 MΩ-input meter reads badly wrong.

Voltage Divider formula

Vout=VinR2R1+R2V_{out} = V_{in} \frac{R_{2}}{R_{1} + R_{2}}
Where
  • VoutV_{out}= Output voltage (V)
  • VinV_{in}= Input voltage (V)
  • R1R_{1}= Upper resistance (Ω)
  • R2R_{2}= Lower resistance (Ω)
Revised 16 October 2026
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formula.expert. (2026, October 16). Voltage Divider Formula & Calculator. https://formula.expert/solvers/voltage-divider

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