🏎️ Power-to-Weight Ratio Calculator
Enter power (hp or kW) and weight (kg or lb) to get the power-to-weight ratio in hp/tonne, W/kg, hp/lb and kW/tonne.
200
hp/tonne
149.1
W/kg
0.09072
hp/lb
149.1
kW/tonne
Power-to-weight ratio is how much power moves each unit of mass — the best single predictor of acceleration. It's shown here as hp per tonne, watts per kilogram, hp per pound and kW per tonne. A hot hatch is around 150 hp/tonne; a supercar 400+; and cycling power is compared in W/kg. 🔒 In your browser.
How the power-to-weight ratio calculator works
Power-to-weight ratio divides an engine's power by the vehicle's mass — how much power there is to move each unit of weight. The tool converts your inputs to consistent units and reports the ratio four common ways: horsepower per tonne, watts per kilogram, horsepower per pound and kilowatts per tonne. A higher ratio means quicker acceleration for a given aerodynamic and traction limit.
Power-to-weight predicts acceleration better than raw power alone — a light car with modest power can out-accelerate a heavy, powerful one. Use kerb (unladen) weight for comparisons, and remember real-world acceleration also depends on traction, gearing, aerodynamics and where in the rev range the power arrives. Cyclists and runners compare fitness the same way, in W/kg.
Frequently asked questions
How do you calculate power-to-weight ratio?
Divide power by weight in consistent units: a 300 hp car weighing 1,500 kg is 300 ÷ 1.5 = 200 hp per tonne. The tool also gives W/kg, hp/lb and kW/tonne.
What is a good power-to-weight ratio?
Roughly: an economy car is 60–90 hp/tonne, a hot hatch around 150, a sports car 200–300, and a supercar 400+. Higher means quicker acceleration, other things being equal.
Why does power-to-weight matter more than horsepower?
Because acceleration depends on force relative to mass. A light car with less power can beat a heavy, powerful one — which is why lightweight track cars feel so fast despite modest engines.
What weight should I use?
Kerb (unladen) weight for like-for-like comparisons, or add passengers and cargo for a real-world figure. Adding weight lowers the ratio and dulls acceleration noticeably.
What is a good W/kg for cycling?
Cyclists compare sustained power in watts per kilogram: recreational riders are around 2–3 W/kg, strong amateurs 4, and professional riders can hold 5–6 W/kg for long efforts. It's the same ratio idea applied to the rider.