Two resistors in series divide a voltage (in the UK and India it's often called a potential divider). Enter the input voltage and both resistors to get the output voltage, the current and the power in each resistor.
Or work backwards: enter the voltage you need, for example 5 V down to 3.3 V for an ESP32 pin, and get standard resistor pairs ranked by accuracy.
How to use
- Enter Vin and the resistors R1 (between the input and the output) and R2 (between the output and ground).
- Read Vout, the current and the power in each resistor.
- Under Find resistors for a voltage, enter the voltage you need and pick the series. The total resistance range keeps the current low without making the output too weak.
- Tap a result to load it into the calculator above.
Voltage divider formula
Vout = Vin × R2 ÷ (R1 + R2). With 10 kΩ and 10 kΩ, the output is half the input. With R1 = 5.1 kΩ and R2 = 10 kΩ, 5 V becomes 3.31 V.
When not to use a divider
A divider only works with light loads: whatever you connect to the output acts as a resistor in parallel with R2 and pulls the voltage down. It's fine for reading a sensor or shifting a logic level; to power a circuit, use a voltage regulator.