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03 Engines and Motion

Car Power to Weight Ratio Calculator

Card No. 03·0020 · Updated · Standard formula, shown below

Weight per horsepower 11.67 lb/hp
Horsepower per 1,000 lb
85.71 hp
Result
Kilowatts per tonne
140.9 kW/t
Result
Engine power
300 hp
You entered
You enter
Engine power, Vehicle weight
You get
Weight per horsepower, Horsepower per 1,000 lb, Kilowatts per tonne
Rounding
2 dp · 1 dp

This calculator finds a car’s power-to-weight ratio from its horsepower and its weight in pounds. You get pounds per horsepower, horsepower per 1,000 lb and the metric kilowatts per tonne, so cars listed in either system can be compared.

Formula

Weight per horsepower = weight ÷ power; horsepower per 1,000 lb = power ÷ weight × 1000. In metric units, kW per tonne = (hp × 0.745699872) ÷ (lb × 0.45359237 ÷ 1000).

  • hp: engine power (mechanical horsepower)
  • lb: vehicle weight in pounds, with or without the driver (be consistent)

Worked Example

A 300 hp car weighing 3,500 lb.

  1. 3500 ÷ 300 = 11.67 lb per hp
  2. 300 ÷ 3500 × 1000 = 85.71 hp per 1,000 lb
  3. 300 hp × 0.7457 = 223.71 kW; 3500 lb × 0.45359237 = 1,587.6 kg = 1.5876 t
  4. 223.71 ÷ 1.5876 = 140.9 kW/t

Limits and common mistakes

  • Lower lb/hp means quicker acceleration, all else equal; traction, gearing and aerodynamics also matter.
  • European “PS” (metric horsepower) is 0.7355 kW, about 1.4% less than one hp.
  • Curb weight excludes the driver; add about 150-200 lb for a driver-included figure.
Formula used
in hp | Engine power | hp | 300 | 0 | 20000
in lb | Vehicle weight | lb | 3500 | 0 | 200000
out lbhp | Weight per horsepower | lb/hp | lb / hp | 2
out hpk | Horsepower per 1,000 lb | hp | hp / lb * 1000 | 2
out kwt | Kilowatts per tonne | kW/t | hp * 0.745699872 / (lb * 0.45359237 / 1000) | 1

Each line is one input (in, sel, list) or one result (out: label, unit, formula, decimals). How the calculators work

Photo collage: a plain unbranded sports car on a quiet race track, and a close-up of its alloy wheel.
Save this card: a 1000 × 1500 image of Car Power to Weight Ratio Calculator.

Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.

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