The displacement or size of an engine is measured in cubic centimeters (cc). Horsepower (hp) is a measurement of the power that engine can produce. So there is no direct relation between the horsepower of an engine and its displacement.
However, as a rule of thumb, small engines like those found on lawn mowers and generators are usually around 125cc, while larger engines found in cars can range from 1,500cc to over 6,000cc.
