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) 

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)