Voltage Divider Calculator
Enter Vin, R1, R2 to calculate Vout instantly, or specify desired output to find the best E24 resistor pairs. Includes load resistance compensation and interactive circuit diagram.
Common Presets
Input Values
Circuit Diagram
Result
What is a Voltage Divider?
A voltage divider is a simple circuit that uses two resistors (R1 and R2) in series to reduce a higher voltage to a lower one. The output voltage (Vout) is determined by the ratio of R2 to the total resistance. This calculator helps you find Vout from known resistor values, or find the best resistor pair for a desired output voltage using standard E24 values.
How to Use the Voltage Divider Calculator
- Choose Calculate mode to find Vout from R1 and R2, or Find Resistors mode to search for ideal pairs
- Use common presets like 5Vβ3.3V or 12Vβ5V for quick setup
- Enter Vin, R1, and R2 values β the output voltage, current, and power are calculated instantly
- Optionally enable load resistance to see its effect on the output voltage
- In Find Resistors mode, enter Vin and desired Vout to get E24 standard resistor pair suggestions
Frequently Asked Questions
How does load resistance affect a voltage divider?
Load resistance appears in parallel with R2, reducing the effective R2 value and lowering the output voltage. This calculator accounts for load resistance by computing the parallel combination of R2 and RLoad to give you the true output voltage.
What are E24 standard resistor values?
E24 is a series of 24 preferred values per decade (1.0, 1.1, 1.2, ..., 9.1) available in 5% tolerance. These are the most commonly available resistors at electronics suppliers.
Why is the voltage divider formula Vout = Vin Γ R2 / (R1 + R2)?
The formula comes from Ohm's Law. The same current flows through both resistors in series, and the voltage across R2 is proportional to R2's share of the total resistance. This makes Vout = Vin Γ R2 / (R1 + R2).