Enter the source voltage (volts), the resistance 1 (ohms), and the resistance 3 (ohms) into the calculator to determine the Thevenin Voltage. 

Thevenin Voltage Formula

The following formula is used to calculate the Thevenin Voltage.

Va-b = Vs * R3 / (R1+R3)
  • Where Va-b is the Thevenin Voltage (volts)
  • Vs is the source voltage (volts) 
  • R1 is the resistance 1 (ohms) 
  • R3 is the resistance 3 (ohms) 

To calculate thevenin voltage, multiply the source voltage by the 1st resistance, then divide by the sum of the 1st and 3rd resistances.

How to Calculate Thevenin Voltage?

The following example problems outline how to calculate the Thevenin Voltage.

Example Problem #1

  1. First, determine the source voltage (volts). In this example, the source voltage (volts) is determined to be 10 .
  2. Next, determine the resistance 1 (ohms). For this problem, the resistance 1 (ohms) is measured to be 3 .
  3. Next, determine the resistance 3 (ohms). In this case, the resistance 3 (ohms) is found to be 4.
  4. Finally, calculate the Thevenin Voltage using the formula above: 

Va-b = Vs * R3 / (R1+R3)

Inserting the values from above into the equation gives: 

Va-b = 10 * 3 / (3+4) = 4.28(volts)

Example Problem #2

Using the same method as above, determine the variables required by the equation. For this example problem, these are provided as follows: 

source voltage (volts) = 50

resistance 1 (ohms) = 5

resistance 3 (ohms) = 6

Entering these given values into the calculator above yields:

Va-b = 50 * 5 / (5+6) = 22.72 (volts)