Voltage Divider Calculator
Calculate Voltage Divider values for science, physics, chemistry, and engineering problems.
This voltage divider calculator finds the output voltage across one of two resistors connected in series, a common circuit technique for scaling down a voltage to a lower level.
Enter the input voltage and both resistor values, and the calculator returns the output voltage across the second resistor.
Worked Calculation Examples
| Scenario | Result | Calculation Step |
|---|---|---|
| Vin=9V, R1=1kΩ, R2=2kΩ | Vout = 6V | Vout = 9 × (2 ÷ (1+2)) = 9 × 0.667 = 6V. |
| Vin=5V, R1=10kΩ, R2=10kΩ | Vout = 2.5V | Vout = 5 × (10 ÷ (10+10)) = 5 × 0.5 = 2.5V - equal resistors always split the voltage exactly in half. |
The Voltage Divider Formula
Vout = Vin x (R2 / (R1 + R2)), where Vin is the input voltage, and R1 and R2 are the two resistors in series, with Vout measured across R2. The output voltage is always a fraction of the input voltage, proportional to R2's share of the total resistance.
Why Voltage Dividers Are Used
Voltage dividers are commonly used to scale a higher voltage down to a level a sensor or microcontroller input can safely read, or to create a reference voltage from a single supply - though they're not efficient for supplying significant current, since the divider itself always dissipates some power as heat.
How to Use the Voltage Divider Calculator
- Open the Voltage Divider Calculator and enter the values requested in the input fields.
- Check the units, percentages, dates, or time periods before reading the answer.
- Review the instant result and adjust any value to compare another scenario.
- Use the formula, example, and FAQs below to understand how the voltage divider calculator works.
Frequently Asked Questions
What is the voltage divider formula?
Vout = Vin x (R2 / (R1 + R2)), where R1 and R2 are two resistors in series and Vout is measured across R2.
What is a voltage divider used for?
It's commonly used to scale down a higher voltage to a lower, safer level for sensors or microcontroller inputs, or to create a reference voltage from a single power supply.
Does a voltage divider work well for powering a load?
Not efficiently - a voltage divider's output voltage changes if a significant current is drawn from it, and it wastes power as heat, so it's best suited for low-current signal or reference applications rather than powering a load directly.
How do I use this voltage divider calculator?
Enter the known values, review the units or settings, and the calculator updates the result instantly. The formula and example on this page show how the answer is produced.
What does the Voltage Divider Calculator calculate?
Calculate Voltage Divider values for science, physics, chemistry, and engineering problems. It is designed for fast browser-based calculations without sign-up, downloads, or manual spreadsheet setup.
What formula does this voltage divider use?
The formula is: Vout = Vin × (R₂ ÷ (R₁ + R₂)). This circuit is a direct application of Ohm's law combined with Gustav Kirchhoff's 1845 voltage law, which states that the sum of voltage drops around any closed loop in a circuit must equal the total supplied voltage - since the same current flows through both series resistors, the voltage across each resistor divides proportionally to its resistance value, which is exactly what the voltage divider formula calculates.
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Last updated: September 27, 2026.