CC to Horsepower Calculator

There is no fixed conversion, because horsepower depends on far more than displacement. This calculator uses the rule of thumb HP = displacement in cc divided by a cc-per-hp ratio. For example, a 160 cc engine at 15 cc/hp estimates about 10.7 hp. Pick the ratio that matches your engine class for a closer guess.

Displacement is the swept volume of the cylinders, but actual power also depends on compression ratio, induction (naturally aspirated vs. turbo or supercharged), valvetrain, fuel, ignition timing, and the RPM the engine runs at. Two engines of the same cc can differ widely in output. The cc-per-hp ratio is a shortcut, not a law of physics, so treat the result as a ballpark.

For small air-cooled 4-stroke utility engines (mowers, generators, pressure washers), about 15 cc/hp is a common starting point and is the default here. A general small-engine baseline is around 16 cc/hp, mild naturally aspirated car engines sit near 17 cc/hp, and many small 2-stroke handheld engines run closer to 32 cc/hp on a displacement basis. Adjust the ratio to match your engine.

It depends on the ratio you choose, since cc equals horsepower times the cc-per-hp ratio. At 15 cc/hp, one horsepower corresponds to roughly 15 cc. At 16 cc/hp it is about 16 cc, and so on. Higher-performance engines make more power per cc, so they use a smaller cc-per-hp ratio.

Multiply mechanical horsepower by 0.7457 to get kilowatts, since 1 hp equals 745.6999 watts. The calculator shows the kW figure automatically. For example, 10.7 hp is about 7.98 kW.

No. It is an approximation for quick estimates and comparisons, not a substitute for a measured dyno figure or the manufacturer's published rating. If you need an exact number, check the engine's spec sheet or have it measured on a dynamometer.