Power Converter
Convert between watts, kilowatts, megawatts, gigawatts, horsepower, BTU/hr, calories per second, refrigeration tons, dBm and more. This power converter is useful for electricity, appliances, engines, heating and cooling systems, engineering checks and quick comparisons between mechanical, thermal and electrical power units.
Convert power
Choose a category or use all units together. The calculator converts your input into watts first, then converts that watt value into every other power unit on the page. This keeps electrical, mechanical and thermal power conversions consistent.
Quick references
Full conversion table
Enter a power value above to see all conversions.
Running cost calculator
Estimate how much it costs to run an appliance at your power rating.
UK Ofgem price cap rate: ~24.5p/kWh (2025). Check your bill for your exact tariff.
Common appliance power ratings
Typical wattages for household appliances — click any row to load it into the converter.
Real-world power reference
From a single LED to the Sun itself.
Types of horsepower
There are several definitions of "horsepower" — here's how they differ.
Conversion formulas
How it works
Power is the rate at which energy is transferred, used or produced. This converter uses watts as the base unit because 1 watt is exactly 1 joule per second.
When you enter a value, the calculator converts it into watts first, then divides by the watt value of each target unit. This allows mechanical horsepower, thermal BTU/hr, electrical kilowatts, dBm and refrigeration tons to be compared through one consistent base unit.
Formula used
converted value = power in watts ÷ watt factor of target unit
Common reference values include: 1 kW = 1,000 W, 1 MW = 1,000,000 W, 1 mechanical hp ≈ 745.7 W, 1 metric hp ≈ 735.5 W, 1 BTU/hr ≈ 0.293 W, and 1 tonne of refrigeration ≈ 3,516.85 W.
Worked example
Example: convert 100 hp to kW
Mechanical horsepower is approximately 745.7 watts.
74,569.987 W ÷ 1,000 = 74.57 kW
So, 100 mechanical hp is about 74.57 kW.
Example: 2 kW appliance for 3 hours
Power becomes energy when it is used over time.
energy = 6 kWh
So, a 2 kW appliance running for 3 hours uses 6 kWh.
Common mistakes
Confusing power and energy
Watts and kilowatts measure power. Watt-hours and kilowatt-hours measure energy used over time.
Assuming all horsepower is identical
Mechanical horsepower, metric horsepower, electrical horsepower and boiler horsepower use different definitions.
Using appliance rating as continuous use
Many appliances do not draw their maximum rated power continuously. Heaters, fridges and air conditioners often cycle on and off.
Ignoring power factor
VA and watts are only equal when the power factor is 1. AC electrical systems may need power factor for accurate real power.
Common questions
What is 1 watt?⌄
How many watts are in 1 horsepower?⌄
Is kW the same as kWh?⌄
Why include dBm?⌄
Sources, assumptions and disclaimer
This converter is for general education, study, household estimates and engineering checks. It uses fixed conversion factors where possible. Results are rounded for readability, so use appropriate significant figures and official references for professional, billing or safety-critical work.
- Base unit: most conversions are handled through watts.
- Power definition: 1 W = 1 J/s.
- Horsepower: different horsepower definitions are included separately because they are not identical.
- VA and kVA: treated as equivalent to watts only where power factor is 1; real AC systems may differ.
- Running cost: cost estimates assume constant power draw and the electricity rate entered by the user.
- Disclaimer: this page does not replace calibrated measurement, electrical design, manufacturer specifications, safety standards or professional engineering advice.