Potential Divider Calculator
Work out the exact output voltage, current, and power dissipation of any two-resistor potential divider circuit. Enter your supply voltage and resistor values to see the full working instantly.
Circuit Values
Enter your supply voltage and resistor values to calculate the divider output
The total supply voltage applied across both resistors.
Vout is measured across R2, between R2 and ground.
Your Divider Output
Vout, current, power, and full working
Enter your supply voltage and resistor values above and click Calculate Output Voltage to see the divider’s output voltage, current, and power.
The Theory Behind a Potential Divider
A potential divider splits a supply voltage between two resistors connected in series. Because the same current flows through both resistors, the voltage across each one is proportional to its resistance, giving a simple and predictable way to scale a voltage down.
📐 The Divider Formula
The output voltage is taken across R2, the resistor connected to ground or the reference node. It depends only on the ratio of R2 to the total resistance, not on the absolute resistor values.
Vout = Vin × R2 ⁄ (R1 + R2)
Doubling both resistors while keeping the same ratio leaves Vout unchanged, but it does change the current drawn and the power dissipated.
🔌 Current and Power
The same current flows through R1 and R2 since they’re in series. Once you know Vin and the total resistance, Ohm’s law gives the current, and the power dissipated by each resistor follows from there.
I = Vin ⁄ (R1 + R2)
Lower total resistance gives a “stiffer” divider that resists loading effects, but it also wastes more power and draws more current from the supply.
Common Potential Divider Ratios
These are typical R1:R2 ratios used to scale a 12V or 5V supply down to common reference and logic-level voltages. Values shown assume an unloaded divider.
| Vin | R1 : R2 Ratio | Vout | Typical Use |
|---|---|---|---|
| 12V | 1 : 1 | 6V | Mid-rail bias |
| 12V | 1 : 2 | 8V | Sensor scaling |
| 12V | 2.2k : 1k | 3.75V | 3.3V logic reference |
| 5V | 1 : 1 | 2.5V | Mid-rail bias |
| 5V | 2 : 3 | 3V | Sensor level shifting |
| 9V | 1 : 2 | 6V | Battery monitoring |
| 3.3V | 1 : 1 | 1.65V | ADC reference |
Potential Divider FAQ
Everything you need to know about potential dividers, the divider formula, and how loading affects real circuits.
A potential divider, also called a voltage divider, is a simple circuit made from two or more resistors connected in series across a voltage supply. It splits the input voltage between the resistors in proportion to their resistance, allowing you to produce a smaller, predictable output voltage from a larger supply voltage.
The output voltage across the second resistor is Vout = Vin x R2 / (R1 + R2), where Vin is the supply voltage, R1 is the resistor closest to the supply, and R2 is the resistor connected to ground or the reference point where the output is measured.
Choose the ratio of R1 to R2 to set the desired output voltage using the divider formula, then pick the overall resistance high enough to limit current draw and power loss, but low enough that any connected load does not significantly affect the voltage at the output node.
Connecting a load resistor in parallel with R2 reduces the effective resistance at the output node, which lowers the output voltage from the value predicted by the simple unloaded divider formula. This effect, known as loading, becomes more significant when the load resistance is similar in size to R2.
A potential divider uses resistors in series to split a voltage, with the output voltage proportional to resistance. A current divider uses resistors in parallel to split a current, with the current through each branch inversely proportional to its resistance, meaning the smaller resistor carries more current.
Potential dividers are widely used to scale down sensor signals for microcontroller inputs, set bias voltages for transistors, create reference voltages, and build sensing circuits with components like thermistors, light-dependent resistors, and potentiometers.