How to Convert Power
Enter the value you want to convert in the Value field.
Select the unit you are converting from in the From list.
Select the unit you want to convert to in the To list.
The result appears instantly below the unit selectors.
Key Features
76 Units Covered
Supports SI watt prefixes (attowatt to exawatt), all major horsepower variants, BTU-based rates, calorie-based rates, foot pound-force, electrical units (VA, kVA), and joule/second SI prefix variants.
Precise Results
Each unit is stored as an exact multiplier relative to the watt. Results use up to 10 significant figures and switch to scientific notation automatically for extreme values.
Works Offline
All conversions run entirely in your browser. No internet connection is needed after the page loads.
Privacy-First
No data is ever sent to a server. Your values stay on your device.
Privacy & Security
This tool runs entirely in your browser. No values are transmitted to any server, stored, or logged. It is safe to use with sensitive data or in offline environments.
Frequently Asked Questions
How accurate are the conversions?
Each unit is defined by an exact multiplier relative to the watt. The conversion formula is: result = value × (from unit in watts) ÷ (to unit in watts). Results are shown to 10 significant figures before trailing zeros are removed.
What is the base unit used for conversions?
All conversions go through the watt as the base unit. Each unit is stored as its value in watts, so any pair can be converted directly without a lookup table.
What is the difference between mechanical and metric horsepower?
Mechanical horsepower (hp) equals 745.69987 W and is defined as 550 foot-pound-force per second. Metric horsepower (PS / Pferdestarke) equals 735.49875 W and is defined as the power needed to raise 75 kg by 1 metre per second.
What is the difference between Btu (IT) and Btu (th)?
The IT (International Table) BTU equals exactly 1055.056 J/s for the per-second variant. The thermochemical BTU (th) equals 1054.35 J/s. The difference is about 0.067% and matters in precision engineering and calorimetry.
Why does the result show scientific notation?
Scientific notation is used automatically when the result is smaller than 1×10⁻⁶ or larger than 1×10¹⁵. This keeps the output readable for extreme conversions such as attowatts to exawatts.
Are volt ampere and watt the same?
In DC circuits, 1 VA = 1 W. In AC circuits they differ: watts measure real power while volt amperes measure apparent power (which includes reactive power). This converter treats them as equivalent (1 VA = 1 W) since it converts magnitudes only.