Power-to-Weight Ratio
Calculator
Compare mechanical horsepower per US short ton, kilowatts per metric tonne and pounds per horsepower from vehicle power and race-ready weight.
Your setup
Your results
CalculatedHigher power per unit mass means more available power relative to inertia, but does not specify traction or acceleration.
Excludes drag, traction, power curves, transmission and rotational inertia.
How the calculation works
Follow the formula and keep the input units consistent at every step.
kW/tonne = power(kW) / mass(kg) × 1000; hp/US ton = HP / (W_lb/2000); lb/hp = W_lb/HP- Use the same load condition for weight comparisons.
- Convert power and mass to the requested units.
- Divide power by mass, or invert for weight per horsepower.
A Worked Example
400 hp and 3,200 lb give 8 lb/hp and 250 hp per US short ton. A US ton is 2,000 lb; a metric tonne is 1,000 kg.
What Your Result Means
Higher power per unit mass means more available power relative to inertia, but does not specify traction or acceleration.
Assumptions & Limitations
Excludes drag, traction, power curves, transmission and rotational inertia.
Common Mistakes
Do not compare hp/US ton with hp/metric tonne as if they were the same unit.
Questions about this calculation
Which values should I enter?
Use the same load condition for weight comparisons. Do not compare hp/US ton with hp/metric tonne as if they were the same unit.
How should I interpret the result’s precision?
Displayed results are rounded for readability. Intermediate calculations retain floating-point precision; extra displayed decimals do not improve your input accuracy.
Can I use metric units?
Yes. Select Metric above the calculator to convert your inputs. Results always state their units. Tire-size designations keep their conventional mm and inch units.
What are the main limitations?
Excludes drag, traction, power curves, transmission and rotational inertia.
Method, sources & relevant guides
Power and rate of work; mechanical horsepower conversion follows 550 ft·lbf/s.
NASA Glenn — What is power?Method documentation updated October 18, 2026. Independent professional review has not been claimed. Read the calculation and review policy.