Engine CC to HP Calculator
*Estimation based on selected engine efficiency ratio.
How to Convert CC to HP
Understanding the relationship between Cubic Centimeters (CC) and Horsepower (HP) is essential for anyone dealing with small engines, motorcycles, or lawn equipment. While there is no direct, fixed mathematical constant to convert displacement to power, automotive experts use specific ratios based on engine design.
The Rule of Thumb: For most small utility engines, the common ratio is 15cc to 17cc = 1 HP. However, this changes drastically based on whether the engine is a 2-stroke or a 4-stroke, and how efficiently it is tuned.
Why CC Does Not Always Equal HP
Displacement (CC) measures the internal volume of the engine cylinders. Horsepower (HP) measures the work the engine performs over time. Several factors influence how much power an engine generates from its size:
- Engine Cycle: 2-stroke engines typically produce more power than 4-stroke engines of the same size because they fire once every revolution.
- RPM: An engine running at higher revolutions per minute (RPM) will generally produce more horsepower.
- Fuel Delivery: Fuel-injected engines are more efficient than carbureted ones.
- Cooling: Liquid-cooled engines can be tuned more aggressively than air-cooled engines.
Common CC to HP Conversion Examples
| Engine Displacement | Average 4-Stroke HP | Average 2-Stroke HP |
|---|---|---|
| 50cc | ~3.3 HP | ~5.0 HP |
| 125cc | ~8.3 HP | ~12.5 HP |
| 250cc | ~16.7 HP | ~25.0 HP |
| 600cc | ~40.0 HP | ~60.0 HP |
The Math Behind the Calculator
The formula used in this calculator is:
HP = CC / Efficiency Ratio
Where the ratio ranges from 8 (high-performance racing engines) to 17 (standard utility engines like lawnmowers).