Understanding voltage in electrical circuits is Important for engineers, hobbyists, and anyone working with electronics. One of the simplest yet most powerful tools in electronics is the voltage divider.
This basic circuit allows you to scale down a larger input voltage into a smaller, more manageable output voltage. Whether you’re designing a sensor interface, conditioning signals, or biasing transistors, the voltage divider is a go-to solution.
Use our free Voltage Divider Calculator below to quickly determine the output voltage for any given set of resistor values and input voltage.
Voltage Divider
Calculate output voltage for resistive dividers, with or without load.
Calculation Steps
What is a Voltage Divider?
A voltage divider is a passive circuit made up of two resistors connected in series. It takes an input voltage (
) and divides it into a smaller output voltage (
) based on the ratio of the resistors. This simple configuration is widely used in electronics for tasks like:
- Signal conditioning
- Sensor interfacing
- Biasing transistors
- Scaling voltages for microcontrollers
How to Use the Voltage Divider Calculator
Our Voltage Divider Calculator is designed to be simple and accurate, even for beginners. Follow these steps to get started:
- Enter Input Voltage (
): The voltage you’re starting with (e.g., 12V). - Input Resistor Values: Enter the values for
(upper resistor) and 
(lower resistor). - Add Load Resistance (Optional): If your circuit has a load, enter its resistance (
). - Choose Units: Select appropriate units (V, mV, kV, Ω, kΩ, MΩ).
- Calculate: Get instant results with detailed steps.
(upper resistor) and Voltage Divider Formula Explained
The formula for calculating the output voltage () of a voltage divider is:
![\[ V_{out} = \frac{V_{in} \times R_2}{R_1 + R_2} \]](https://diyprojectslabs.com/wp-content/ql-cache/quicklatex.com-2a9cfd4ce14e8847cc067a4da676e4a0_l3.png "Rendered by QuickLaTeX.com")
Where:
: Output voltage (what you want)- : Input voltage (source voltage)
- : Upper resistor value (Resistance 1)
- : Lower resistor value (Resistance 2)
Voltage Divider with Load Resistance
When a load resistor (
) is connected, the output voltage decreases due to loading effects. To account for this, we calculate the equivalent resistance (
) of 
and in parallel:
![\[ R_{eq} = \frac{R_2 \times R_L}{R_2 + R_L} \]](https://diyprojectslabs.com/wp-content/ql-cache/quicklatex.com-34a3247676305990393e474c9bbdf46c_l3.png "Rendered by QuickLaTeX.com")
The output voltage is then calculated as:
![\[ V_{out} = V_{in} \times \frac{R_{eq}}{R_1 + R_{eq}} \]](https://diyprojectslabs.com/wp-content/ql-cache/quicklatex.com-2b209c6c4a2083be61f6069512417f70_l3.png "Rendered by QuickLaTeX.com")
Advanced Concepts: Loading Effects
When connecting a load to a voltage divider, the output voltage often drops due to loading effects. The actual output voltage becomes:
![\[ V_{out} = V_{in} \times \frac{R_2 || R_L}{R_1 + (R_2 || R_L)} \]](https://diyprojectslabs.com/wp-content/ql-cache/quicklatex.com-9d1fd0bd5772196dbe291cc57b8ec7ba_l3.png "Rendered by QuickLaTeX.com")
Where 
represents the parallel resistance:
![\[ R_2 || R_L = \frac{R_2 \times R_L}{R_2 + R_L} \]](https://diyprojectslabs.com/wp-content/ql-cache/quicklatex.com-5f63ee3fe1eb399bfe7ceaef51f8deed_l3.png "Rendered by QuickLaTeX.com")
Important Tip: Always consider power dissipation in your resistors. The power dissipated in each resistor can be calculated using:
![\[ P = I^2 \times R \quad \text{or} \quad P = \frac{V^2}{R} \]](https://diyprojectslabs.com/wp-content/ql-cache/quicklatex.com-5d385a8b79c5ab9b0c40b4186cabc6a7_l3.png "Rendered by QuickLaTeX.com")
Example Calculation
Basic Voltage Divider
Given:
- R1 = 4 kΩ
- R2 = 8 kΩ
- Vin = 12V
![\[ V_{out} = \frac{12 \times 8}{4 + 8} = 8 \, \text{V} \]](https://diyprojectslabs.com/wp-content/ql-cache/quicklatex.com-d64a7fbdb4aed4ce38c4e1b33e903626_l3.png "Rendered by QuickLaTeX.com")
Voltage Divider with Load
Given:
- RL = 6 kΩ
- R1 = 4 kΩ
- R2 = 8 kΩ
- Vin = 12V
First, calculate the equivalent resistance ():
![\[ R_{eq} = \frac{8 \times 6}{8 + 6} = 3.43 \, \text{k}\Omega \]](https://diyprojectslabs.com/wp-content/ql-cache/quicklatex.com-19f05f018e6a68b31193566d0f87fb42_l3.png "Rendered by QuickLaTeX.com")
Then, calculate the output voltage ():
![\[ V_{out} = \frac{12 \times 3.43}{4 + 3.43} = 5.54 \, \text{V} \]](https://diyprojectslabs.com/wp-content/ql-cache/quicklatex.com-6bb1ed26e00f79a4a96bdacff9a17f98_l3.png "Rendered by QuickLaTeX.com")
