What is a good power-to-weight ratio?

Under 100 BHP/tonne is low (economy cars). 100-200 is moderate (GTI-type hot hatches). 200-300 is fast (sports cars). 300+ is very fast (supercars). A Lotus Elise achieves 200+ BHP/tonne with relatively modest power.

Why does power-to-weight matter more than just power?

A 200 BHP car weighing 1000kg accelerates much faster than a 200 BHP car weighing 2000kg. Power-to-weight ratio is the fairest way to compare acceleration potential between different cars.

Should I use kerb weight or including driver?

For comparison with manufacturer figures, use kerb weight (no driver/fuel). For real-world performance, add 75kg for a driver and half a tank of fuel. This gives a more realistic picture.

What is wheel horsepower (WHP)?

Wheel horsepower is the power actually delivered to the wheels after drivetrain losses. A typical manual gearbox and differential lose about 15% of engine power. Automatic transmissions may lose 18-20%. WHP is what actually accelerates the car.

How do I improve my power-to-weight ratio?

You can either add power (ECU remap, intake, exhaust) or reduce weight (remove spare wheel, lighter wheels, strip interior). Weight reduction is often cheaper and also improves handling, braking, and fuel economy. A 10% weight reduction has the same effect as a 10% power increase.

CarCalcs

Power to Weight Calculator

Calculate power-to-weight ratio in BHP per tonne.

Power

Power in BHP

Kerb Weight

Vehicle weight (check V5 document)

How We Calculate This

Divides engine power by vehicle weight in tonnes. Also shows estimated wheel horsepower (assuming 15% drivetrain loss).

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Actual figures may vary based on driving conditions, vehicle specifications, and other factors.