Electrical Power Calculator
Calculate electrical power using voltage and current (P = V × I), or voltage and resistance, or current and resistance.
Enter any two values to calculate power.
Enter any two values to calculate power.
Electrical Power Formulas
P = V × I
P = V² / R
P = I² × R
P = V² / R
P = I² × R
Example: A 120 V outlet supplying 2 A of current.
P = 120 × 2 = 240 W
P = 120 × 2 = 240 W
Understanding Power
- Power measures the rate of energy transfer.
- 1 watt = 1 joule per second.
- Higher power means more energy used per unit time.
Common Power Ratings
| Device | Typical Power |
|---|---|
| LED bulb | 7–15 W |
| Laptop | 30–65 W |
| Microwave | 700–1200 W |
| Space heater | 1500 W |
| Hair dryer | 1000–1800 W |
FAQ
What is the difference between watts and kilowatts?
1 kilowatt (kW) = 1000 watts. Your electricity bill is in kilowatt-hours (kWh), which is power × time.
Does higher wattage mean more electricity cost?
Yes. Cost = Power (kW) × Time (hours) × Rate ($/kWh). A 100 W device running 10 hours uses 1 kWh.
Last updated: 2026-08-08