What Is a Good Power-to-Weight Ratio?

Benchmarks from economy cars to Top Fuel, what the figure actually predicts, and the three things it completely ignores.

Last updated 1 August 2026 · 6 min read

↓ Benchmarks ↓ Which units ↓ What it predicts ↓ What it ignores ↓ FAQ

Power-to-weight is the closest thing to a single number that describes how quick a vehicle is. It works because acceleration is force divided by mass — the physics is right there in the ratio. But it is routinely quoted in four different units and two opposite directions, which makes comparison harder than it should be.

Quick benchmark: under 10 lb per horsepower feels genuinely fast on the road. Under 5 lb/hp is supercar territory.

Benchmark Figures

Using kerb weight and quoted crank power. Add a driver and fuel for a realistic figure — that alone worsens most road cars by 5–7%.

Category	lb/hp	kg/hp	hp/tonne	Typical 0–60
Economy hatchback	25–30	11–14	73–88	10–12 s
Family saloon	15–20	7–9	110–147	8–10 s
Hot hatch	10–13	4.5–6	170–220	5.5–7 s
Sports car	7–9	3.2–4.1	245–315	4–5.5 s
Supercar	4–6	1.8–2.7	370–550	2.8–3.8 s
Superbike	2–3	0.9–1.4	735–1,100	2.5–3 s
Top Fuel dragster	0.05	0.02	44,000	~0.8 s

The jump from supercar to superbike is the one that surprises people. A litre superbike weighing 200 kg with 200 hp has a ratio no road car can approach — which is why bikes out-accelerate almost anything to about 100 mph, and why they stop gaining beyond that as aerodynamics take over.

Which Units, and Which Direction?

Four conventions are in common use, and two of them run in opposite directions:

lb/hp or kg/hp — weight per unit of power. Lower is better. Standard in drag racing.
hp/ton or bhp/tonne — power per unit of weight. Higher is better. Standard in UK and European motoring press.
kW/kg or W/kg — metric power per weight. Higher is better. Used in motorsport engineering and cycling.

Watch the ton, too. A US short ton is 2,000 lb; a metric tonne is 2,205 lb; a UK long ton is 2,240 lb. Quoting "hp per ton" without saying which introduces a 10% spread. Our power-to-weight calculator and weight-to-power calculator cover both directions.

What the Ratio Actually Predicts

Straight-line acceleration, and it does so well. Two cars with the same lb/hp will run broadly similar quarter-mile times regardless of how they reach that figure — a light car with a modest engine and a heavy car with a big one end up close.

It also scales sensibly. Halving the ratio does not halve the 0–60 time, because drag and traction limits intervene, but the relationship is consistent enough that experienced racers estimate ETs from it directly.

Three Things It Completely Ignores

Traction. Power that cannot reach the road does nothing. An all-wheel-drive car with a worse ratio routinely beats a rear-drive car off the line on a cold or damp surface. This is the single biggest gap.
Aerodynamics. Drag rises with the cube of speed, so above roughly 100 mph frontal area and drag coefficient dominate. A brick-shaped van and a sleek coupé with identical ratios diverge sharply at speed.
Where the power arrives. Peak power says nothing about the shape of the curve. An engine making its power in a narrow band near the redline needs constant gear changes; a broad torque curve does not.

Gearing sits underneath all three. A gearbox multiplies torque, so identical engines with different final drives accelerate differently despite identical ratios on paper.

Improving the Ratio

Both halves of the fraction are available, and weight is usually the cheaper one. Removing 10% of a car's mass improves the ratio as much as adding 11% more power — and unlike power, weight reduction also improves braking, cornering and tyre wear.

This is why serious track builds start with weight before touching the engine. Adding power to a heavy car with standard brakes and tyres frequently makes it slower around a lap, not faster.

To estimate performance from your figures, try our quarter mile calculator or 0–60 time calculator.

How this guide is sourced

Benchmark ranges are representative of production vehicle categories using kerb weight and quoted crank horsepower, and are intended for orientation rather than as specifications for particular models. Unit conversions use 1 lb = 0.45359237 kg and 1 US short ton = 2,000 lb. Quoted 0-60 ranges are typical for each category and vary with traction, gearing, conditions and test methodology. Top Fuel figures are widely published nominal values.

Frequently Asked Questions

What is a good power-to-weight ratio for a car?

Under 10 lb/hp feels genuinely fast — roughly 220 hp per tonne. Sports cars sit at 7–9 lb/hp, supercars 4–6.

Is a higher or lower power-to-weight ratio better?

Depends on direction. hp per tonne: higher is better. lb per hp: lower is better. Check units before comparing.

How do you calculate power-to-weight ratio?

Divide power by weight (or weight by power for the inverse). A 3,200 lb car with 400 HP is 8 lb/hp, or 250 hp per US ton.

Do motorcycles have better power-to-weight than cars?

Dramatically. A litre superbike at ~200 kg and 200 hp reaches 2–3 lb/hp. That advantage fades above about 100 mph as drag dominates.

Why does a car with a worse ratio sometimes win?

Traction, usually. Power that cannot reach the road does nothing — an AWD car launches harder than a RWD car with a better ratio. Gearing and aerodynamics also matter.

Should I use kerb weight or weight with driver?

Use weight with driver and fuel. Kerb weight often excludes both, and adding them typically worsens the ratio by 5–7%.

Is it better to add power or remove weight?

Removing weight, usually. Taking off 10% of mass improves the ratio as much as adding 11% more power — and it also improves braking, cornering and tyre wear.