Electrical Power Calculator

Calculate the power drawn by a device from its voltage and current.

How the Math Works

The Electrical Power Calculator uses two fundamental formulas from Ohm's Law to determine electrical quantities. Power (P) is calculated by multiplying voltage (V) by current (I), expressed as P = V × I, which tells us the rate of energy consumption in watts. Resistance (R) is found by dividing voltage by current, written as R = V ÷ I, revealing how much a component opposes the flow of electricity in ohms. These relationships form the backbone of electrical circuit analysis and allow precise calculations when two of the three values are known.

Practical Applications

To use this calculator, simply enter any two known values - voltage in volts and current in amperes - and the calculator will compute the missing values. For example, if you know a device operates at 120 volts and draws 2 amps, the calculator will determine it uses 240 watts of power and has a resistance of 60 ohms. This tool is essential for electrical engineers designing circuits, technicians troubleshooting systems, or students learning basic electronics principles.

Day-to-Day Use

Understanding electrical power helps you make informed decisions about energy consumption and safety in everyday life. When choosing appliances, you can estimate monthly electricity costs by calculating power usage over time. For home projects, knowing resistance values helps you select appropriate wire gauges and circuit breakers to prevent overheating. This knowledge also enables you to troubleshoot why circuits might trip breakers or why certain devices run hotter than others, making you a more informed consumer and DIY enthusiast.

Worked example

120 V × 5 A = 600 W (resistance 24 Ω).

FAQ