Resistor Wattage Calculator

Resistor Wattage Calculator

Resistor Wattage Calculator

Resistor Wattage Calculator will help you to easily calculate the wattage of resistor.

For calculations of Resistors for Voltage Divider please visit, Resistor Voltage Divider Calculator.

For calculations of Parallel Resistors please visit, Parallel Resistor Calculator.

Enter the values of Voltage and Current and press "Calculate" to get answer and "Reset" to clear.


An excel sheet you can download by clicking below download button, which you can use any time in your mobile or in your laptop.

Resistors are mostly used electronic component in the electronic circuits. Proper selection of resistor type and resistance value will help you to control the current perfectly.

Resistors limits or control the current to pass across them. Heat is generated as a result, when the current passes through the resistor. Resistor will burn if generated heat crosses the permitted limit.

As the heat starts to generate from the resistor, it starts to loose it’s characteristics. And finally to control this generated heat we have to use heat sink.

But placement of heat sink increases cost and sometimes increases the complexity in the PCB.

But we can solve this issue by selecting proper wattage of the resistor.

Resistor Wattage Calculator
Different wattage of resistor

Resistors can have wattage ranges that start from 0.05 watts to 150W. Sometimes higher wattage ranges also available as per application requirement.

For calculating wattage, we have to use Ohm’s law along with voltage and resistance.

As per Ohm's law;

R = V / I

R = Resistance

We can write the formula as;

I = V / R

Formula for wattage i.e. power is
P = V * I

P = Power
V = Voltage
I = Current

By using Ohm’s law in the power formula, we will get;

P = (V * V) / R

Having a resistor with double wattage would be good because temperature will degrade the power handling capacity of the resistor. Also, check this big size of resistor fits in your PCB.


High current handling many times is the requirement of the circuit. The adverse effect of heating of resistor can be control by proper wattage selection of resistor.

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