Power to Weight Ratio Explained
Understand why Power to Weight Ratio (PWR) is the single most important metric for vehicle acceleration and how it affects performance on the road and track.
What is Power to Weight Ratio?
Power-to-weight ratio (PWR) is a calculation commonly applied to engines and movable power sources to enable the comparison of one unit or design to another. It is effectively the specialized coefficient that determines how fast a vehicle can accelerate.
"For every kilogram of weight, how much power is available to move it?"
Why It Matters More Than Horsepower
Marketing brochures love to shout about horsepower. "400 Horsepower!" sounds impressive, but if that 400hp engine is inside a 3,000kg truck, it won't be fast. Conversely, 200hp in a 800kg Lotus Elise is thrilling.
"Adding power makes you faster on the straights. Subtracting weight makes you faster everywhere." — Colin Chapman, Lotus Founder
A vehicle with a better power-to-weight ratio accelerates faster, brakes in shorter distances, and changes direction more eagerly. This is why motorcycles are often faster than supercars in a straight line; they have very little weight to move.
∑ How to Calculate It
Divide power by weight. Common formats:
- Imperial: Horsepower per Ton (hp/ton)
- Metric: Kilowatts per Tonne (kW/t)
- Cycling: Watts per Kilogram (W/kg)
⚡ Real World Benchmarks
- Economy Car ~80 hp/ton
- Hot Hatch ~180 hp/ton
- Supercar ~500 hp/ton
- Formula 1 ~1,300 hp/ton