Power-to-Weight Ratio Calculator
Find the power-to-weight ratio of any vehicle, motor or athlete in W/kg, kW/tonne and hp/tonne — enter power in kW, hp or PS and mass in kg or lbs.
Power unit
Mass unit
Watts of power per kilogram of mass
- 1
Power in watts
150 kW × 1,000 = 150,000 - 2
Mass in kg
1,200 kg = 1,200 - 3
Power-to-weight ratio
150,000 ÷ 1,200 = 125Watts of power per kilogram of mass.
How does this calculator work?
Power-to-weight ratio = power (W) ÷ mass (kg). Enter power in kW, hp, PS or W and mass in kg or lbs; the calculator converts to SI and returns results in W/kg, kW/tonne, hp/tonne and hp/short-ton. City cars fall around 50–100 W/kg; supercars exceed 250 W/kg.
Formula
How this is calculated
Power-to-weight ratio (also called specific power) measures how much power is available per unit of mass. A higher ratio means faster acceleration and better performance for vehicles, or greater aerobic output for athletes. The standard SI unit is watts per kilogram (W/kg), but engineers also use kilowatts per metric tonne (kW/t — numerically equal to W/kg) and horsepower per ton (hp/tonne for metric, hp/short-ton for US).
To compare across different unit systems the calculator first converts your inputs to SI (watts and kilograms) using the standard factors: 1 hp = 745.7 W, 1 PS (metric horsepower) = 735.5 W, 1 lb = 0.4536 kg. It then computes the ratio and re-expresses it in all common forms.
Performance benchmarks vary by year and model but approximate 2024 figures are: city cars around 40–70 W/kg, family cars 70–120 W/kg, sports cars 120–200 W/kg, supercars 200–350 W/kg and hypercars or racing vehicles above 350 W/kg. Elite cyclists can sustain about 6 W/kg and sprint briefly to 20 W/kg. These reference values are editable estimates — consult manufacturers for exact specifications.
Frequently asked questions
Power-to-weight ratio is the amount of engine or motor power divided by total mass. A higher ratio means the vehicle or machine can accelerate more quickly and climb hills more easily, because more force is available per kilogram to overcome inertia and gravity.
1 metric tonne = 1 000 kg ≈ 2 205 lbs. 1 US short ton = 2 000 lbs ≈ 907 kg. Horsepower per metric tonne is the international engineering convention; hp per short ton is used in some US publications. The calculator shows both.
Context matters: for road cars, >150 W/kg is considered sporty, and >250 W/kg puts you in supercar territory. Elite bicycle racers average ~6 W/kg in time trials. Fighter jets exceed 1 000 W/kg (thrust-to-weight >1). These are approximate 2024 reference figures.
Also known as
TG we-Calculate Editorial Team. (2026). Power-to-Weight Ratio Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/power-to-weight-ratio-calculator
TG we-Calculate Editorial Team. "Power-to-Weight Ratio Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/power-to-weight-ratio-calculator.
TG we-Calculate Editorial Team, "Power-to-Weight Ratio Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/power-to-weight-ratio-calculator
@misc{wecalculate_power_to_weight_ratio_calculator, title = {Power-to-Weight Ratio Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/power-to-weight-ratio-calculator}}, year = {2026}, note = {TG we-Calculate} }
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