I don't consider hp to be a factor to determine if it is a compact tractor or lawn mower. I define a compact tractor as a machine that has live hydraulics, a lift cylinder, most cases a diesel , water cooled engine that is built for longevity(not a throw away like many lawn mowers), is driven by a mechanical or fluid drive(not belts). & usually engine ,transmission, & rear end are all part of the frame (not an engine, transmission, & rearend bolted to a steel frame). The compact tractor is a shrunk down version of a farm tractor. There are 25 hp lawn mowers that can't do the work of a 15hp compact or last any where near as long. Since I've farmed all my life, I questioned what they could do when I first got involved with compact tractors . I'm a firm believer in them now