Pounds per horsepower and kilograms per kW
Weight to HP Ratio Calculator
Drag racers speak in pounds per horsepower: the lower, the quicker. Enter weight and horsepower and get lb/hp along with kg/hp and kg/kW, plus the quarter-mile time that ratio implies.
- kg per kW
- 5.32 kg/kW
- kg per PS
- 3.91 kg/PS
- lb per kW
- 11.73 lb/kW
- Quarter-mile ET
- 12.00 sec
Why lb/hp is the drag racer’s ratio
The quarter-mile formula depends only on weight divided by horsepower, so lb/hp translates directly into time. At 8.75 lb/hp the ET is about 12.00 s. Halve the ratio and you cut ET by about 21%.
Pounds per hp to quarter-mile time
| lb per hp | 1/4 mile ET | Trap speed |
|---|---|---|
| 5.0 | 9.96 s | 136.8 mph |
| 6.0 | 10.58 s | 128.8 mph |
| 7.0 | 11.14 s | 122.3 mph |
| 8.0 | 11.65 s | 117.0 mph |
| 9.0 | 12.12 s | 112.5 mph |
| 10.0 | 12.55 s | 108.6 mph |
| 12.0 | 13.34 s | 102.2 mph |
| 14.0 | 14.04 s | 97.1 mph |
| 16.0 | 14.68 s | 92.9 mph |
Lowering the ratio
You can improve the ratio by adding power, removing weight or both. A 100 lb weight cut on a 3,500 lb, 400 hp car is worth about the same as 12 hp at the same weight. Because horsepower costs far more per unit than pounds removed, weight reduction is often the cheaper route.
Frequently asked questions
How do I calculate weight to hp ratio?
Divide weight in pounds by horsepower. For metric, divide kilograms by kW or by PS.
What is a good lb/hp?
Under 8 lb/hp is very fast on the street, under 5 is supercar territory, and over 14 is relaxed.
Does lb/hp predict quarter-mile time?
Yes. The formula uses nothing else. See the quarter mile calculator.
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