Zener Diode Calculator

Summary

Enter supply voltage, Zener voltage, and load current to instantly get the series resistor value and power ratings for a Zener regulator circuit.

How it works

1. Enter the supply voltage (Vs) — the unregulated DC input to your regulator.
2. Enter the Zener voltage (Vz) — the desired regulated output voltage (from the diode datasheet).
3. Enter the load current (IL) — the current your load draws at Vz.
4. Optionally set a Zener test current (Izt) to ensure the diode stays above its minimum operating current.
5. Click Calculate to see the series resistor value, Zener current, and power dissipation for both components.
6. Use the nearest standard E24 resistor value shown as a starting point for your design.

Use cases

• Design a simple 5 V or 3.3 V reference voltage for a microcontroller circuit.
• Clamp a signal line to a safe voltage level with a Zener shunt.
• Protect a sensitive circuit from overvoltage by selecting the right Zener and resistor.
• Verify an existing Zener regulator design against component power ratings.
• Size components for a low-current voltage reference in an op-amp bias circuit.
• Teach or learn Zener regulator theory with instant numerical feedback.
• Check whether a 0.5 W or 1 W Zener diode is sufficient for your power budget.
• Calculate component values when substituting a different Zener voltage in a design.

Frequently Asked Questions