Voltage Divider

Vout = Vin × R2 / (R1 + R2)

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Result
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Formula

Vout = Vin × R2 / (R1 + R2)

Description

A voltage divider is a simple two-resistor circuit that produces an output voltage that is a fraction of the input voltage. It is one of the most common subcircuits in electronics, used for biasing transistors, creating reference voltages, interfacing sensors, and scaling signals down to levels safe for ADC inputs on microcontrollers. The output voltage depends only on the ratio of R2 to the total resistance, not their absolute values, though lower values waste more current and higher values are more susceptible to noise.

Variables

  • Vin — Input voltage in volts (V)
  • R1 — Upper resistor connected to Vin (Ω)
  • R2 — Lower resistor connected to ground (Ω)
  • Vout — Output voltage taken across R2 (V)

Practical Notes

This formula assumes no load on the output. Any load in parallel with R2 reduces the effective lower resistance and drops Vout. For high-impedance loads like op-amp inputs or MOSFET gates this effect is negligible, but for low-impedance loads you must account for the parallel combination of R2 and the load.

Related Formulas

Ohm's Law Electrical Power Current Divider Thévenin Equivalent Norton Equivalent Temperature Coefficient of Resistance

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