Voltage Divider Calculator - Vout, Resistor Values & Standard E24/E12 Picks
Voltage Divider Calculator
Find Vout, or the resistor you need for a target voltage
Three Ways to Solve
Find Vout from two resistors, or find R1 or R2 for the output voltage you want.
Real Resistor Values
Get the nearest standard E24 or E12 value and the output voltage you would actually see with it.
Current and Power
See the current the divider draws and the power in each resistor, to check they are safe and not wasteful.
Full Privacy
Everything is calculated in your browser.
How a Voltage Divider Works
Two resistors in series share the input voltage in proportion to their resistance: Vout = Vin × R2 ÷ (R1 + R2), taken across R2. With 12 V across two equal 10 kΩ resistors, Vout is 6 V and the divider draws 0.6 mA. To get 5 V from 12 V with R1 = 10 kΩ you need R2 = 10 kΩ × 5 ÷ 7 = 7.14 kΩ, and the nearest E24 value is 7.5 kΩ.
A divider is only accurate when the load draws far less current than the divider itself, because any load in parallel with R2 lowers Vout. Use it to scale a signal for a sensor or ADC input, not to power a load. Keep the resistors' power ratings well above the calculated dissipation, and remember that real 5% or 10% resistors shift the output slightly.
Key Takeaways
- Friendly input: Type 10k, 4.7k, 1M or 4k7 instead of long numbers.
- Standard values: E24 and E12 series are built in.
- Load caution: Explains why a loaded divider drifts.