Definition
A unit of power equal to 75 kilogram-meters per second, or approximately 735.5 watts. Metric horsepower is slightly smaller than the mechanical (imperial) horsepower of 550 foot-pounds per second, which equals about 745.7 watts.
Plain English
A measurement of engine power used in countries on the metric system. It is close to, but not exactly the same as, the horsepower number commonly used in the United States.
Context Anchor
Seen in engine specifications, maintenance references, and aircraft or engine data from countries that use metric-based power ratings.
Derivation
Horsepower was originally defined by James Watt to compare steam-engine output to the work of draft horses. The metric version was later created so the unit could be expressed in metric measures (kilograms and meters) instead of feet and pounds. The two definitions don't quite match because they were built from different base units.
Why Pilots Care
Engine power may be listed in metric horsepower on imported or international aircraft, requiring conversion for accurate performance calculations and weight-and-balance planning.
Intuition Check
Do not assume metric horsepower and U.S. horsepower are identical. Metric horsepower is slightly smaller, so the number must be converted when exact power comparison matters.
Example Sentence 1
The European-built engine was rated at 180 metric horsepower, which converts to roughly 178 imperial horsepower.
Example Sentence 2
After converting the metric horsepower rating to imperial units, the pilot confirmed the aircraft met the required climb performance.