Zener diode power rating calculator is an online electronic tool to measure the values of Power Rating, Resistance Value and Resistance Power Rating. When the normal PN junction diode operates in reverse breakdown voltage, the current through the junction and the power dissipated at the junction will be high. The normal diode will get damaged in such reverse biasing. Whereas, the Zener Diode is a special type of PN junction diode with adequate power dissipation capabilities to operate in the breakdown region. Zenor doide normally used under reverse bias conditions. Zener Diode is heavily doped than ordinary diodes. The breakdown voltage depends upon the doping level. If the diode is heavily doped the breakdown occurs under reverse biasing at the lower breakdown voltage and vice versa. The sharp current increasing under breakdown conditions is due to Avalanche Breakdown and Zenor Breakdown. The diode can be widely used as a voltage regulator. To designing the electronic circuits along with Zenor diodes, the resistance and power rating calculation is necessary. By using this Online Zener Diode Power Rating Calculator, one can easily calculate the resistor value, power rating and resistor power rating based on the input values of Source Voltage, Output Voltage and Maximum Current.