Power-to-Weight Ratio Calculator
Works out power-to-weight in the four common forms, and places the figure on the scale from economy car to supercar.
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The formula
kW/t = power (kW) ÷ weight (kg) × 1,000 kg/hp = weight ÷ (kW × 1.341)
Acceleration is force over mass, and the force an engine can deliver scales with its power, so power divided by mass is the first-order predictor of how quickly a vehicle gets going. It says nothing about traction, gearing or aerodynamics, which is why it predicts 0–60 only roughly.
What to watch out for
Rough bands, in kW per tonne, at running weight:
- Under 60 — small economy cars.
- 60–100 — most family cars.
- 100–180 — hot hatches and sports cars.
- 180–300 — serious performance cars.
- 300 and up — supercars; a litre sports bike is around 500.
Use the weight with a driver and fuel in it. Manufacturers quote kerb weight dry or with a nominal driver, and the difference is 5–8% of the ratio.
Frequently Asked Questions
How do I calculate power-to-weight ratio?
Divide power by weight. 200 kW in a 1,500 kg car is 133 kW per tonne, or about 5.6 kg per horsepower. In US terms that is roughly 162 hp per ton.
What is a good power-to-weight ratio for a car?
Over 100 kW/t feels quick; over 180 is a genuine performance car. A typical family hatchback is 60–90.
Does reducing weight help as much as adding power?
For this ratio, 100 kg off a 1,500 kg car equals about 7% more power — and lighter also brakes, corners and stops better, which added power does not.