Here’s What a Power to Weight Ratio Means for Car Buyers

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Posted on 09 August 2015 by Keith Griffin 

                               

 

When researching performance figures of new cars, you may have come across the statistic for power to weight ratio. What is power to weight ratio? Basically, the measure of what makes a small engine car powerful and a big-engine beast docile.

 

You take a vehicle’s horsepower and divide it by its curb weight. That gives you the power to weight ratio, which is represented as horsepower to 1 lb. The higher the number, the better your car is going to be in terms of performance. In effect, look for cars with horsepowers to weight above 1. It’s explained below.

The website measurespeed.com has an easy-to-use power to weight calculator. Simply plug in a vehicle’s curb weight and its horsepower and it gives you the number. For my purposes I researched the 2015 Alfa Romeo 4C Spider and input its 237 horsepower and 2,487 curb weight for a power to weight ratio of .95 hp to 1 lb.

 

Let’s look at a Bentley Continental GTC with a V8 engine. It puts out 500 horsepower with a curb weight of 5,478 lbs. That means it has a power to weight ratio of .91 hp to 1 lb. By that measure, the Alfa Romeo 4C Spider is going to be the better car.

But neither car meets the golden standard of 1 hp to 1 lb. Start to reach that number and you’re getting into some truly sporty cars.
Who makes that list? At 1.58 hp to 1 lb., the 2015 Dodge Challenger Hellcat finds itself as probably one of the top Americans. Overall, it’s going to be hard to beat the 2016 McLaren 675 LT with its power to weight ratio of .229 hp to 1 lb.

Is power to weight ratio the be-all and end-all of performance? Not necessarily because it doesn’t reflect a car’s handling or braking ability.

But if you are looking to narrow down your choices, it’s not a bad place to start. Plus, it makes you sound more knowledgeable to your friends if you can quote your car’s power to weight ratio. I won’t be sharing the number for my 2008 Mazda Mazda5 any time soon but I did drive a 2015 Lamborghini Huracan (shown above) recently. Its power to weight ratio is .195 hp to 1 lb.