Power Calculator

This calculator will determine the electrical power dissipated by a resistive element.

The application of this calculator (Figure 1) is for determining power loss across resistive circuit elements in a simple electrical system. This calculator may be useful when calculating total system power loss and when trying to understand voltages and currents at different nodes within a circuit.


Ohms law for a simple, resistive circuit.

Figure 1. Ohm's Law creates a simple, resistive circuit.


Power Equation

To find the power dissipated by a resistive circuit element, we can use any of the following equations. 


$$P = VI = I^{2}R = \frac{V^2}{R}$$



P = Power dissipated in a resistive element

V = The voltage drop across the resistive element

I = The current through the resistive element


Using this equation, we can solve for any two variables given the other two.

For example, given the power and current, we can solve for the resistance and voltage by rearranging the equations as follows:


$$R = \frac{P}{I^2}$$


$$V = \frac{P}{I}$$


Further Reading

Textbook—Basic DC Circuit Theory

Textbook—Standard Resistor Power Ratings