Power-to-Weight
Horsepower per ton, pounds per horsepower, and what a diet is worth.
Units
Power measured at
PLANNED MODS optional: see before and after
11.00 lb per hp: properly quick.
lb per hp11.00
hp per tonne200
kg per hp4.99
W per kg149
Using crank power and curb weight.
WHAT A DIET IS WORTH
Every 100 lb you take out does the same for power-to-weight as adding about 9 hp.
| REMOVE | SAME AS ADDING | NEW LB/HP |
|---|---|---|
| 50 lb | 5 hp | 10.83 |
| 100 lb | 9 hp | 10.67 |
| 200 lb | 19 hp | 10.33 |
| 300 lb | 30 hp | 10.00 |
KNOW THE TERMS
- Power-to-weight
- How much weight each horsepower has to move. It predicts acceleration better than horsepower alone, though gearing, traction and aero matter too.
- lb/hp vs hp/tonne
- Same idea, opposite way round. Lower lb/hp is better; higher hp per tonne is better. A tonne here is a metric tonne, 1,000 kg.
- Crank vs wheel power
- Spec sheets quote power at the crankshaft. A chassis dyno measures at the wheels, typically 10–20% lower after drivetrain losses.
- Curb weight
- The car with all fluids and a full tank, no driver or cargo. Add the driver for what the car actually carries.
ASSUMPTIONS
- The ratio uses peak power. Two cars with the same ratio can still feel different: torque curve, gearing and traction all matter.
- The diet equivalence compares power-to-weight only. Lighter cars also brake, turn and wear consumables better, which no horsepower adds.
- The bands (sporty, properly quick…) are rough orientation, not a ranking.