Horse Measurement Terms
Equines are measured in units. Which unit of measure is used depends on the association doing the registration. Some registries use inches to determine size, since it is easier than trying to convert to hands. Other registries record measurements in hands. A hand is four inches.
Horsepower (HP) is the name of several units of measurement of power. The most common definitions equal between 735.5 to 746 watts. The horsepower is not recognized in the International System of Units (SI).
The horsepower was originally defined to compare the output of steam engines with the power of draft horses.