Electrical Power Calculator (P = IV)
Electrical Power Calculator
Electrical power measures how fast energy is consumed or produced in a circuit. It is measured in watts (W) and is fundamental to sizing circuits, wires, and power supplies.
Conversion Formula
P = IV is the base formula. Combined with Ohm's Law (V=IR), we get P = V²/R and P = I²R.
Step-by-Step Examples
V=120V, I=5A = P=600W
120 × 5 = 600 watts
V=240V, R=60Ω = P=960W
240² / 60 = 960 watts
I=3A, R=50Ω = P=450W
3² × 50 = 450 watts
History
The watt is named after James Watt, the Scottish inventor who improved the steam engine. The unit was adopted by the Second Congress of the British Association for the Advancement of Science in 1882.
Common Use Cases
- Sizing circuit breakers
- Calculating energy consumption
- Designing power supplies
- Selecting wire gauge
Frequently Asked Questions
What is electrical power?
Electrical power is the rate at which electrical energy is transferred by a circuit, measured in watts (W).
How do I calculate power?
Use P = I × V (current times voltage). You can also use P = V²/R or P = I²R if you know resistance.
What is the difference between watts and kilowatts?
1 kilowatt (kW) = 1,000 watts (W). Kilowatts are used for larger power ratings like appliances and motors.
How do I convert watts to amps?
Divide watts by voltage: I = P / V. For example, 600W at 120V = 5 amps.
What is a typical home circuit power rating?
A standard 15-amp, 120V circuit can handle 1,800 watts. A 20-amp circuit can handle 2,400 watts.