How to Convert CC to HP for Small Engines

by Joe FriedmanUpdated July 07, 2023
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Measuring power output can give you the horsepower (HP) of a car. The rule is that the higher the engine’s CC (engine displacement) is, the higher the engine’s power output is. This is what an HP rating means – it’s engine horsepower. Higher CC means a higher HP conversion and thus a higher horsepower rating.

The relationship between cubic centimeters (cc) and horsepower (hp) is complex and depends on many factors. First of all, it's important to note that cc is a measure of engine size, while hp is a measure of how much power it produces. Generally, a larger engine will produce more power, but the ratio isn't uniform across all engines. Engines for lawn mowers and snowblowers are different engines than industrial engines. Car engines are a different type of engine than ATV engines or turbocharged engines. It depends on how well-tuned the engine is as well as the type of fuel it uses. Most modern passenger cars, however, do fall into a small range of ratios.

It’s just a measure of power with different units of measurement that lets you know what the fuel economy and engine capacity are of the combustion chamber. The compression ratio of the pistons and specs of an HP engine as well as the CC rating tell you about the metrics of the engine. Here’s how to convert CC to HP for small engines without using an HP calculator. You can use a conversion chart based on engine design and fuel type, but these are the general rules for internal combustion engines to convert HP.

1. Divide the cc of the engine by 15.

Divide the cc of the engine by 15. For example, the 1800 cc of a 1.8-liter 16V Ford Escort's engine divided by 15 yields 120 hp.

2. Divide the cc of the engine by 17

Divide the cc of the engine by 17. For example, the Escort's 1800 cc divided by 17 yields approximately 106.

3. Horsepower falls somewhere in the range

Recognize the horsepower falls somewhere in the range established by the previous steps. In fact, the Escort's horsepower is 115. Its cc to hp ratio is 15.6522.

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