Watts Calculator
Calculate electrical power in watts and convert between power units
Watts Calculator
Calculate watts (electrical power) from volts and amps, volts and ohms, or amps and ohms. Convert watts to kilowatts, megawatts, horsepower, BTU/h, and more. Enter any two known values to find the power in watts.
โก Enter Known Values
๐ Power Result
๐ Common Appliance Wattage Reference
| Appliance | Watts (W) | Kilowatts (kW) | Amps @ 120V |
|---|---|---|---|
| ๐ก LED Light Bulb | 10 | 0.01 | 0.08 |
| ๐ก CFL Light Bulb | 15 | 0.015 | 0.13 |
| ๐ป Laptop Computer | 65 | 0.065 | 0.54 |
| ๐ฅ๏ธ Desktop Computer | 300 | 0.30 | 2.50 |
| ๐บ Television (55") | 120 | 0.12 | 1.00 |
| โ๏ธ Refrigerator | 150 | 0.15 | 1.25 |
| โ Coffee Maker | 1,000 | 1.00 | 8.33 |
| ๐ณ Toaster | 1,200 | 1.20 | 10.00 |
| ๐ฅ Space Heater | 1,500 | 1.50 | 12.50 |
| ๐ Hair Dryer | 1,800 | 1.80 | 15.00 |
| โก Electric Oven | 2,500 | 2.50 | 20.83 |
| ๐ Central A/C | 3,500 | 3.50 | 29.17 |
| ๐ Clothes Dryer | 5,000 | 5.00 | 41.67 |
๐ Understanding Watts
What is a Watt?
A watt (W) is the SI unit of power, named after James Watt. It is defined as one joule of energy per second. In electrical terms, one watt equals one volt multiplied by one ampere (1 W = 1 V ร 1 A).
Watts vs Kilowatt-Hours
Watts measure instantaneous power, while kilowatt-hours (kWh) measure energy consumed over time. A 100W bulb running for 10 hours uses 1 kWh of energy. Electricity bills are typically charged per kWh.
Sizing Circuits
Knowing the wattage of your appliances helps determine the appropriate circuit breaker size and wire gauge. A standard 15A / 120V circuit can handle up to 1,800W (80% rule: 1,440W continuous).
Watts Calculation Formulas
Watts can be calculated from different combinations of electrical quantities. The relationship between power (P), voltage (V), current (I), and resistance (R) is governed by Ohm's Law and the power equations.
Three Key Formulas
Watts = Volts ร Amps
Watts = Voltsยฒ รท Ohms
Watts = Ampsยฒ ร Ohms
Unit Conversions
Kilowatt to watt
Megawatt to watt
Mechanical horsepower to watt
Watt to BTU per hour