A handy engineering utility that solves for voltages or resistor values in a common voltage divider circuit. Enter three terms (out of Vin, Vout, R1 or R2) and this app will solve for the fourth term automatically. The resistor picker will only let you pick from actual resistor values that exist. It’s a great time saving tool for quickly selecting resistor values in a switching power supply design or any other circuit that incorporates a voltage divider.

When solving for a voltage, select two resistor values and one of the voltages. The remaining voltage will be displayed automatically. The max and min possible voltages will also be displayed based on the resistor tolerances. The current and power through the divider will be displayed at the bottom of the screen.

When solving for a resistor value, select two voltages and one resistor value. The remaining resistor value will be displayed in yellow. This is an ideal value. Use the resistor picker to select an actual resistor value close to that ideal value. You can then tell the app to solve for Vin or Vout to see if the resulting voltage meets your design requirements.