# Voltage Divider Calculator

URL: https://speedycalculator.com/calculators/physics/voltage-divider/
Last updated: 2026-10-25

> The voltage divider calculator finds the output voltage of two resistors in series across a supply, Vout = Vin × R₂ ÷ (R₁ + R₂), along with the current through the divider.

## Inputs

- Input voltage (V, mV, kV)
- R₁ (top) (Ω, kΩ, MΩ)
- R₂ (bottom) (Ω, kΩ, MΩ)

## Results

- Output voltage
- Divider current
- Power in divider

## Formula

```
Vout = Vin × R₂ ÷ (R₁ + R₂)
```

## Explanation

Voltage dividers scale a voltage down, for example to read a battery voltage with a microcontroller.

### How to use the Voltage Divider Calculator

- **Input voltage**
- **R₁ (top)**
- **R₂ (bottom)**
- Want to work backwards? Type a value into **Output voltage** and **R₂ (bottom)** is calculated for you.

Results update as you type, and every field accepts the units shown in its menu.

### How it works

The output voltage is the fraction of the supply dropped across the lower resistor.

### Inputs explained

FieldWhat to enterInput voltageUnits: V, mV, kVR₁ (top)Units: Ω, kΩ, MΩR₂ (bottom)Units: Ω, kΩ, MΩ

### What each result means

- **Output voltage** = [Input voltage] × [R₂ (bottom)] ÷ ([R₁ (top)] + [R₂ (bottom)])
- **Divider current** = [Input voltage] ÷ ([R₁ (top)] + [R₂ (bottom)])
- **Power in divider** = [Input voltage]^2 ÷ ([R₁ (top)] + [R₂ (bottom)])

### Example values

How the main result changes when **R₂** changes and everything else stays at the example values above:

R₂ (bottom) (Ω)Output voltage (V)2,3502.28343,5253.12754,7003.83675,8754.44097,0504.96199,4005.8144

## Worked example

Inputs — Input voltage: 12 V; R₁ (top): 10,000 Ω; R₂ (bottom): 4,700 Ω.

Results — **Output voltage = 3.8367 V**; Divider current = 0.000816 A; Power in divider = 0.009796 W.

## FAQ

**Can I power a device from a divider?**
Usually not; the load changes the output. Use a regulator.

**How do I choose resistor sizes?**
Larger values waste less power but are more sensitive to load.

**What formula does the Voltage Divider Calculator use?**
Vout = Vin × R₂ ÷ (R₁ + R₂).

**Can I work backwards from the result?**
Yes. Type the result you want into Output voltage and the calculator finds the matching r₂ (bottom).