Zener Diode Series Resistor Calculator


Zener Diodes come in different power ratings such as 500 mW, 1 W, 2 W. First choose the power rating of the Zener Diode, this depends on the load and its requirement. It's always better to choose a rating slightly higher than needed.

In the boxes below enter the Power(W) rating of the zener diode, and the regulated output voltage (Vz) that you want.

This calculates the maximum current Iz that the zener diode operates at, anything above and it becomes toast.
Power(W):        Vz:                                                   Iz:


In the box below, enter the Input voltage Vs that you want to tame. This will calculate the value of the series resistance Rs you need to use with the Zener.

Vs:                                                                            Rs:

Extra Information (optional)

Do you know the load resistance? Go and find out the resistance of your load if you don't
know, otherwise keep the default of 1 kΩ.

The Load current IL is the amount of current passing through a load of value RL (1 kΩ default).

RL:                                                                               IL:

For a load of value RL (1KΩ default), the supply current Is that will be required to drive the circuit properly is shown below: