Horsepower Converter

What the Horsepower Converter does

Horsepower Converter: 1 hp = 0.74569987 kW, so multiply a horsepower (mechanical) value by 0.74569987 to get kilowatt, or divide to go back. Example: 1 hp = 0.74569987 kW.

Give the Horsepower Converter your Value, From and To and it works out Result, How it was calculated and Reverse conversion. Values update as you type, so comparing options is a matter of editing one field.

Typical users are engineers checking a datasheet. Converting once from the original figure beats chaining approximations.

Because it is all local, the tool is as fast as your device and as private as your own notes.

The field table, the method and a worked example are documented after the tool for anyone who wants to check the working.

What do the Horsepower Converter fields mean?

The Horsepower Converter uses 3 inputs. Nothing is blank on load, so you can see the shape of the answer before supplying your own figures.

How does the Horsepower Converter work?

Both units are converted through power's base unit (W), so any of the 9 units in the dropdowns can be paired in either direction without loss of accuracy.

Every factor here is the defined one, not a textbook approximation. That matters more than it sounds: rounding a factor early is the usual reason two converters disagree in the fourth decimal place.

Worked example

These are the values the Horsepower Converter loads by default, and the result it produces from them. These are the exact values loaded when the page opens, and the answer they produce.

Horsepower: two different units

Mechanical (imperial) horsepower is defined as exactly 745.6998715822702 watts, while metric horsepower (PS, used across much of Europe and Japan) is a separate unit defined as exactly 735.49875 watts, about 1.4% smaller, which matters when comparing vehicle specifications across markets.

Worth knowing

• A car specified at "300 PS" is therefore about 296 mechanical horsepower, not 300: a small but real difference that can matter when comparing performance figures between a US-market listing (hp) and a European one (PS or CV).
• James Watt originated the mechanical horsepower unit in the 1780s specifically to help sell his steam engines, by giving customers an intuitive comparison to the animal labour his engines were replacing: a deliberately practical, marketing-driven origin rather than a scientifically derived one.
• A genuinely useful comparison: a healthy human can sustain roughly 0.1 horsepower over an extended period (a bit more in short bursts), which is part of why a single-horsepower engine already represents a meaningful multiple of unassisted human effort.

Definitions: BIPM SI Brochure · NIST reference on units

How to use it

1. Set Value.
2. Pick a value for From: the options are Milliwatt (mW), Watt (W), Kilowatt (kW), Megawatt (MW), Gigawatt (GW) or Horsepower (mechanical) (hp).
3. Pick a value for To: the options are Milliwatt (mW), Watt (W), Kilowatt (kW), Megawatt (MW), Gigawatt (GW) or Horsepower (mechanical) (hp).
4. Because there is no round trip to a server, updating on every keystroke costs nothing.
5. Check Result, How it was calculated and Reverse conversion on the right.
6. Print gives a tidy version without the navigation, which is handy for attaching to a file.

What this tool does not do

• Conversion factors use SI definitions; some industries use their own rounded factors.
• Repeated conversions compound rounding, so convert once from the original value where possible.
• The tool answers exactly the question it is given; it cannot know the context around your numbers.
• The tool trusts your numbers completely, so a mis-keyed digit propagates straight through.

Frequently asked questions

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