What's the Relationship Between Engine Size and Horsepower?

There is a relationship between engine size and horsepower, as they are both measurements to the power generated by the engine. However, engine size, which is measured in cubic centimeters, measures a different aspect than the horsepower measurement.

A cubic centimeter is the measurement unit used to identify the displacement caused by each piston within a cylinder, measuring the volume swept from the piston's top dead center to its bottom dead center. The pistons inside each cylinder function by transferring the force from the expanding fuel gas in the cylinder into the crankshaft. The greater measurement of cubic centimeters indicates a greater volume of displacement in the combustion chamber.

Horsepower is rate measurement of the engine’s work over a period of time. One horsepower equals 550 foot-pounds per second, or 33,000 foot-pounds per minute. Higher horsepower means an engine can deliver greater power.

While both cubic centimeters and horsepower can measure engine power, they are not directly related. Certain factors can increase horsepower without changing the engine’s displacement, such as the use of turbochargers.

While there is no exact conversion rate between the power generated by 1 horsepower into cubic centimeters, a commonly used rule of thumb is that 15 to 17 cubic centimeters equals 1 horsepower.