Power-to-weight ratio is the best single predictor of acceleration — it normalizes engine output against how much mass it has to move.
Where
| Power | Engine output in hp or kW |
| Weight | Vehicle weight in lb or kg |
Worked example
A 300 hp car weighing 3,500 lb has 300 ÷ 3,500 = 0.086 hp/lb, or about 171 hp per ton.
FAQ
Is power-to-weight ratio a better performance indicator than horsepower alone? For acceleration and general performance feel, yes. A lighter car with less horsepower can outperform a heavier car with more horsepower, which is why power-to-weight ratio is commonly used to compare vehicles across very different weight classes.
Should I use curb weight or weight with a driver and fuel? Curb weight, the empty vehicle, is the standard reference for published specifications, but actual on-road power-to-weight is slightly lower once driver, passengers, and cargo are added.
Use the Power-to-Weight calculator in the automotive calculators.