What is Power-to-Weight Ratio?
A measure of performance comparing an engine's power to the car's weight, often a better guide to acceleration than horsepower alone.
Power-to-weight ratio expresses how much power a vehicle has relative to its mass, usually quoted as horsepower per tonne or kilograms per horsepower. Because acceleration depends on both how much force is available and how much mass must be moved, this ratio is often a more meaningful performance indicator than raw power.
A lightweight car with modest power can out-accelerate a much more powerful but heavier one if its power-to-weight ratio is higher. This is why lightweight sports cars such as the Lotus models and Caterham-style machines feel so fast despite relatively small engines, and why adding power and removing weight are both effective routes to performance.
The principle explains the enthusiast mantra that lightness is a virtue. Reducing weight improves not only acceleration but also braking, cornering and efficiency, which is why serious performance and racing cars obsess over shedding every unnecessary kilogram.
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Power-to-Weight Ratio on the blog
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