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Physics • Power-to-Weight Ratio Calculator

Power-to-Weight Ratio Calculator

Calculate power-to-weight ratio in hp/lb, hp/ton, and kW/kg from engine power and vehicle weight.

hp per lb
0.0857
hp per ton
171.43
kW per kg
0.1409
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Calculation Guide & Reference

Power-to-Weight Ratio Mathematics

Power-to-weight ratio calculator computes hp per pound, hp per ton, and kW per kg from engine power and vehicle weight.

Standardized Mathematical Formula
Power-to-Weight = Power ÷ Weight

Power-to-weight ratio measures how much power is available per unit of mass — a core determinant of acceleration performance in vehicles, engines, and even athletes. A higher ratio generally means quicker acceleration.

Variables:
Power:Engine or motor power, in horsepower (hp)
Weight:Total vehicle (or system) weight, in pounds
How It Works (Step-by-Step)
  • 1Enter the power in horsepower and the weight in pounds.
  • 2View the power-to-weight ratio in hp/lb, hp/ton, and kW/kg.
Real-World Numerical Example
A 300 hp Car Weighing 3,500 lbs

A car produces 300 horsepower and weighs 3,500 pounds.

hp per lb: 300 ÷ 3,500 ≈ 0.0857.
hp per ton: 0.0857 × 2,000 ≈ 171.43.
Result: The car has a power-to-weight ratio of approximately 171.4 hp per ton.
Calculation Best Practices & Tips
Maintain consistent SI units (meters, kilograms, seconds, amperes, volts) across all variables before computing.
Check vector sign conventions (e.g., downward acceleration due to gravity g = -9.80665 m/s²) in projectile motion problems.

Frequently Asked Questions (FAQ)

Economy cars typically run 60-100 hp/ton, sports cars 150-250 hp/ton, and supercars can exceed 400-500 hp/ton — higher generally means faster acceleration.

It's also used for aircraft (thrust-to-weight for climb rate), cycling (watts per kg for climbing performance), and general engineering to compare the efficiency of different power sources relative to their mass.

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