Voltage Divider Calculator

What is the Voltage Divider Calculator?

Calculate the output voltage of a two-resistor voltage divider. A voltage divider uses two resistors to produce a lower output voltage from a higher input, a common trick for sensors and logic-level shifting.

How to use the Voltage Divider Calculator

1. Enter your input voltage, your r1, your r2.
2. Results update automatically as you type; you can also press Calculate.
3. Read the output: output voltage, current.
4. Use the 📊 chart to see the result visually, then copy or share it.

Formula and method

Worked example

With input voltage = 12 V, r1 = 10,000 Ω, r2 = 4,700 Ω, the Voltage Divider Calculator returns output voltage: 3.8367 V; current: 0.8163 mA.

Where the Voltage Divider Calculator helps in real life

A maker wants to read a 5 V sensor signal with a 3.3 V microcontroller. Choosing resistor values in the calculator gives an output just under 3.3 V.

A student analyzes a potentiometer circuit and calculates the output voltage at different settings.

Common mistakes to avoid

• Using a divider to power a load that draws significant current.
• Swapping R1 and R2, which changes the output.
• Ignoring the load’s input resistance.
• Using very low resistor values that waste power.

💡 Practical tip: Voltage dividers are fine for signals but poor at powering loads — use a regulator instead.

Tips for better results

• Use dividers for signals, not for powering devices.
• Choose resistor values in the kilohm range to limit wasted current.
• Measure the output with the real load connected.

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