Resistor Divider Calculator

Solve for any variable using Vout = Vin × (R2 ÷ (R1 + R2)). Enter any three values — Vin, Vout, R1, or R2 — and the app instantly calculates the fourth. Reverse-solve R2 with R2 = (Vout × R1) ÷ (Vin − Vout), or R1 with R1 = R2 × ((Vin ÷ Vout) − 1).

Match your calculated resistor values to standard E24 (5% tolerance, 24 values per decade) and E96 (1% tolerance, 96 values per decade) series. The app lists the closest standard pairs and their resulting error, so you can order real parts from distributors instead of theoretical values.

Estimate worst-case output voltage spread from resistor tolerance (1%, 5%, etc.) and compare against your target. The app shows the percentage error from ideal and flags when a divider is too sensitive for your application — critical for ADC references and sensor scaling.

Account for load resistance RL in parallel with R2, which shifts Vout from its unloaded value. The app calculates the loaded output, divider current, and Thevenin equivalent voltage and resistance — the exact parameters needed for ADC input drive and amplifier biasing.

Enter and read values in standard engineering notation — 4.7k, 10M, 220R — with automatic SI prefix handling. Every calculation is saved to a local history log so you can revisit past designs, compare scenarios, and reuse divider configurations.

Export divider calculations as CSV or share via email and messaging apps. Copy results with full resistor values, tolerance data, and load analysis to paste directly into BOMs, design reviews, or lab notebooks. Fully functional offline with no internet connection required.