PreBuild Engineering
PCB calculators / Circuit design
Free tool · PreBuild Engineering

Voltage divider calculator with standard resistor values

Get a resistor pair you can actually buy, for feedback networks, ADC scaling and level setting.

Inputs

V
V
kΩ
Higher saves power; lower is less sensitive to load and noise

Result

—

Why it matters

An ideal divider rarely uses buyable resistor values. Picking the nearest standard pair and checking tolerance prevents regulators from landing off-target and ADC readings from drifting.

Formula

Vout = Vin · R2 / (R1 + R2) Worst case: R1 and R2 at opposite tolerance limits R_out = R1 ∥ R2

Design tips

  • For regulator feedback, use the bottom resistor value the datasheet recommends and solve for the top.
  • Use 0.1% resistors where the divider sets an accurate reference.

More free calculators

LED series resistorSeries resistor, nearest standard value and power. I²C pull-up resistorValid pull-up range from bus speed and capacitance. Crystal load capacitorsC1/C2 values from crystal load capacitance and stray. RC low-pass filterCutoff, time constant, settling and attenuation. Trace widthMinimum width for a current, copper weight and temperature rise. Trace resistance & voltage dropResistance, IR drop and power loss of a copper trace.

Results are engineering estimates from standard formulas and published approximations. Always confirm against component datasheets, your fabricator's capabilities and, for critical designs, simulation or measurement.