Enter a vehicle's power and weight to get its power-to-weight ratio in hp per tonne, pounds per horsepower and kW per kg. Add a driver or load, estimate wheel power, and build a comparison list of cars, trucks and bikes.
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lb
Added to the weight, in the same unit. Use 0 for curb weight.
lb per hp = weight in pounds ÷ horsepower (lower is quicker, common in the US)
Conversion: lb per hp = 2,204.6 ÷ hp per tonne; kW/kg = hp per tonne × 0.000746
Worked example: a 450 hp coupe weighing 3,500 lb (1,588 kg) has 450 ÷ 1.588 = 283 hp per tonne, or 3,500 ÷ 450 = 7.8 lb per hp, or 335.6 kW ÷ 1,588 kg = 0.211 kW/kg.
Typical power to weight ratios
These are representative round figures for each type of vehicle, not data for a particular model. Use the calculator with the exact spec sheet numbers of the vehicles you are comparing.
Vehicle type
Typical power
Typical weight
hp per tonne
lb per hp
Small city car
75 hp
1,000 kg
75
29.4
Compact hatchback
130 hp
1,300 kg
100
22.0
Midsize sedan
200 hp
1,542 kg (3,400 lb)
130
17.0
Full-size pickup
400 hp
2,359 kg (5,200 lb)
170
13.0
Sports coupe
450 hp
1,588 kg (3,500 lb)
283
7.8
Supercar
650 hp
1,500 kg
433
5.1
125 cc commuter motorcycle
15 hp
140 kg
107
20.6
1000 cc sport bike
200 hp
200 kg
1,000
2.2
Tips for fair comparisons
Match the weight definition. Curb weight, weight with a 75 kg driver, dry weight (motorcycles, no fuel or oil) and wet weight can differ by 10% or more.
Match the power definition. Manufacturer figures are crank (flywheel) power. Dyno sheets usually show wheel power, which is lower because of drivetrain losses.
Electric vehicles often quote peak power that is only available for short bursts, and their batteries make them heavy, so their ratio can look modest while their low-speed acceleration is very strong.
Ratio is not everything. Gearing, traction, launch control, aerodynamics and tires decide real acceleration, which is why the quarter-mile figure here is only an estimate.
Frequently asked questions
How do you calculate power to weight ratio?
Divide the power by the weight. In metric the usual form is horsepower divided by the weight in metric tonnes (hp per tonne), or kilowatts divided by kilograms (kW/kg). For example, 200 hp in a 1,542 kg car is 200 / 1.542 = 129.7 hp per tonne. The US often uses the inverse, weight divided by power: 3,400 lb / 200 hp = 17 lb per hp.
Is a higher or lower power to weight ratio better?
For hp per tonne or kW/kg, higher means more power for every unit of mass and generally quicker acceleration. For the inverse figures, lb per hp or kg per hp, lower is better because each horsepower has less weight to move.
What is a good power to weight ratio for a car?
As a rough guide, many everyday family cars sit around 100 to 150 hp per tonne (about 15 to 20 lb per hp), sporty cars 150 to 250, sports cars 250 to 400 and supercars above 400 hp per tonne. Large trucks and campers can be well under 60. Gearing, traction and aerodynamics also matter, so two cars with the same ratio can feel different.
Should I use curb weight or weight with the driver?
Spec sheets normally quote curb weight (with fluids but no people). For a figure that reflects real driving, add the driver and any passengers or cargo. Some European specs already include a 75 kg driver, so check the definition before comparing numbers from different sources.
How do I convert hp per tonne to lb per hp?
Divide 2,204.6 by the hp per tonne figure. For example, 130 hp per tonne equals 2,204.6 / 130 = 17.0 lb per hp. To go the other way, divide 2,204.6 by the lb per hp value.
Why do motorcycles have such high power to weight ratios?
A motorcycle is very light compared with a car. A 200 hp sport bike weighing about 200 kg has roughly 1,000 hp per tonne, far more than most supercars, although traction and wheelies limit how much of that can be used when accelerating.
What is the difference between hp, PS and kW?
One mechanical horsepower (hp) is 745.7 watts, one metric horsepower (PS) is 735.5 watts and one kilowatt is 1,000 watts. So 100 kW equals 134.1 hp or 136.0 PS. The calculator converts all of them before working out the ratio.
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