Enter the input voltage (volts) and the voltage drop across the resistor (ohms) into the calculator to determine the Zener Voltage. 

Zener Voltage Formula

The following formula is used to calculate the Zener Voltage. 

Vz = Vs – Vr

  • Where Vz is the Zener Voltage (volts)
  • Vs is the input voltage (volts) 
  • Vr is the voltage drop across the resistor (ohms) 

How to Calculate Zener Voltage?

The following two example problems outline how to calculate the Zener Voltage.

Example Problem #1:

  1. First, determine the input voltage (volts). In this example, the input voltage (volts) is measured to be 100.
  2. Next, determine the voltage drop across the resistor (ohms). For this problem, the voltage drop across the resistor (ohms) is calculated to be 30.
  3. Finally, calculate the Zener Voltage using the formula above: 

Vz = Vs – Vr

Inserting the values from above and solving the equation with the imputed values gives: 

Vz = 100 – 30 = 70 (volts)


Example Problem #2: 

Using the same process as example problem 1, we first define the variables outlined by the formula. In this case, the values are:

input voltage (volts) = 145

voltage drop across the resistor (ohms) = 10

Entering these values into the formula above gives : 

Vz = 145 – 10 = 135 (volts)