Power-to-Weight Ratio

Power-to-weight ratio compares how much engine power is available for each kilogram of vehicle mass. It matters because, for a given amount of power, a lighter vehicle can increase its speed more quickly: there is less mass to accelerate, so the same power produces a bigger change in motion. This is why sports cars, race cars, and even some motorcycles are judged not just by horsepower, but by how much weight that power has to move.

Use this formula when comparing the performance potential of different vehicles, especially for acceleration, hill climbing, or track use. It is also useful in design and motorsport when deciding whether a power increase or a mass reduction will improve performance more effectively.

• Using horsepower and kilograms without converting to consistent units
• Dividing mass by power instead of power by mass
• Assuming a higher power-to-weight ratio automatically means a faster top speed, when it mainly relates to acceleration