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MotoWild Lab · Performance and air

Power-to-weight ratio calculator

kW per tonne, hp per tonne and kg per hp, with or without the rider.

Units
kW
kg
kg

Result

kW per tonne526 kW/t
hp per tonne706 hp/t
kg per hp1.42 kg/hp

How it is calculated, with your numbers
  1. Total masstotal = mass + rider200 + 85 = 285 kg
  2. kW per tonnekwt = power / total × 1000150 / 285 × 1000 = 526 kW/t
  3. hp per tonnehpt = power × 1.34102209 / total × 1000150 × 1.34102209 / 285 × 1000 = 706 hp/t
  4. kg per hpkghp = total / (power × 1.34102209)285 / (150 × 1.34102209) = 1.42 kg/hp

Working uses the metric units the formula is written in.

  • power Power (kW)
  • mass Vehicle weight (ready to ride) (kg)
  • rider Rider and gear (kg)
  • total Total mass
  • kwt kW per tonne
  • hpt hp per tonne
  • kghp kg per hp

What it means

Acceleration depends on power relative to the mass being moved. Include the rider: on a motorcycle the rider can be a third of the total, which is why the same bike feels so different with a passenger. Weight "ready to ride" (wet, with fuel) is fairer than dry weight.

Assumptions and limits

  • Crank power as published; power at the wheel is lower.

Sources

  • Gillespie, T. D., Fundamentals of Vehicle Dynamics, SAE International, 1992.

Related calculators

Top speed from power and dragThe speed where aerodynamic drag and rolling resistance use up all the power.Power from torque and rpmConvert torque at an rpm into kW and horsepower.

All calculators in the Lab →