Weight to Horsepower Ratio Calculator

Divide the weight by the horsepower for pounds per hp, or the power by the weight for hp per pound. A car with 290 hp and a weight of 4,069 lb has 14.03 lb per hp, or 0.0713 hp per pound. The calculator gives both.

Use power / weight. In metric, divide watts by kilograms: 400 kW in a 1,500 kg car is 400,000 / 1,500 = 266.7 W/kg. In imperial, divide horsepower by pounds. Choose your units in the calculator and it converts. Choose your units in the calculator and it converts everything for you.

It is power divided by weight, also called specific power. Wikipedia describes it as a calculation commonly applied to engines and mobile power sources to compare one unit or design with another. A higher ratio means more power for each unit of mass.

Wikipedia lists economy cars at roughly 50 to 70 W/kg, common sedans at 85 to 110 and performance cars at 160 to 180. In pounds per hp that is about 33 to 47 for economy cars and 9 to 10 for performance cars. What counts as good depends on what you want.

Performance cars around 160 to 180 W/kg are about 0.10 to 0.11 hp per pound, from Wikipedia's typical values. Common sedans are about 0.05 to 0.07. There is no single good figure, so compare vehicles of the same kind. There is no single good figure, so compare vehicles of the same kind and the same power basis.

At a ratio of 0.1 hp per pound, 100 lbs needs 10 hp, and at 0.2 hp per pound it needs 20 hp. For a whole vehicle, multiply the weight by the ratio you want. The horsepower table lists weights from 400 to 4,500 lb at four ratios.

Most road cars have between about 0.03 and 0.12 hp per pound. Wikipedia's typical values put economy cars near 0.030 to 0.043 and performance cars near 0.097 to 0.109. Calculate your own with the weight and power from the spec sheet.

No. Horsepower is a unit of power, defined as about 745.7 watts, and does not depend on weight. Weight enters when you compare vehicles, because the same power moves a lighter vehicle faster. That is what the power-to-weight ratio shows.

No, it does not change the engine's power, but it raises the power-to-weight ratio. A 300 hp car at 3,500 lb is 11.7 lb per hp, and at 3,200 lb it is 10.7. Removing weight improves the ratio just as adding power does.

Take the reciprocal. 14.031 lb per hp is 1 / 14.031 = 0.0713 hp per pound. The conversion table lists common ratios in five units so you can read across. Divide 1 by the number, and the same step works in reverse for any ratio you meet.

Multiply by 745.7 and divide by 0.45359. So 0.1 hp per pound is 0.1 × 745.7 / 0.45359 = 164.4 W/kg. The calculator shows all the ratio units at once. Use the same factor in reverse to go from W per kg back to hp per pound.

Mechanical horsepower is 745.7 watts. Metric horsepower, PS, is 735.49875 watts, from lifting 75 kg one metre in one second. So 100 PS is 98.6 mechanical hp. Choose PS in the calculator if your spec sheet uses it. Choose PS in the calculator if your spec sheet uses it, because the gap is small but real.

No. One horsepower is a defined amount of power, about 745.7 watts, and was never meant to equal a real horse. Machines are rated against that unit. The calculator treats horsepower as a power unit only, and converts it to watts.

Use whichever you want to compare. Brake horsepower is measured at the crankshaft, while wheel horsepower is lower because of drivetrain losses, as Wikipedia notes. The calculator has a drivetrain loss box if you want to estimate wheel power from engine power.

The loss depends on the vehicle, and no single figure applies. Wikipedia only says wheel power equals shaft power minus the losses in the drivetrain. Leave the box at zero to use the power as quoted, or enter a figure from your own dyno or a trusted source.

For a performance estimate, yes. The extra weight box adds the driver, passengers, fuel or cargo to the curb weight. A 3,600 lb car with a 200 lb driver is 3,800 lb, which turns 500 hp from 7.2 lb per hp into 7.6.

Use watts for power and kilograms for the rider plus bike. A cyclist producing 300 W at 75 kg is 4.0 W/kg. Wikipedia cites a professional climber at 6.7 W/kg. Choose watts and kilograms in the calculator. Choose watts and kilograms in the calculator, and include the bike in the weight.

Wikipedia gives about 145 W/kg for cruisers and about 143 W/kg for dual-sport motorcycles. That is about 0.088 hp per pound. Motorcycles often have a much higher ratio than cars, because they weigh less for the power. Motorcycles often have a much higher ratio than cars, because they weigh less for the power they make.

Not by itself. It indicates acceleration potential, but real speed also depends on traction, gearing, aerodynamics and tires. Wikipedia notes a vehicle's ratio equals its acceleration times its velocity, so it describes capability, not a time or top speed. Use it to compare capability, and then look at real test results for times and top speed.

At 160 to 180 W/kg, Wikipedia's performance range is about 9.1 to 10.3 lb per hp. A 400 hp car at 3,600 lb is 9.0 lb per hp. Lower is more powerful for the weight. Use your own car's weight and power to see where it sits in that range.

Multiply the weight by the hp per pound you want. For 0.15 hp per pound in a 3,000 lb car you need 450 hp. Or divide the weight by the target pounds per hp, so 3,000 / 10 = 300 hp.

Multiply the horsepower by the pounds per hp you want. A 300 hp engine at 10 lb per hp suits 3,000 lb. The weight table lists totals from 6 to 16 lb per hp for a 300 hp car, with the matching W/kg.

They may use different horsepower definitions, count weight differently, or use a different unit. Mechanical and metric horsepower differ by about 1.4 percent, and curb weight differs from weight with driver. Check the unit and weight basis on each. Always read which basis a calculator is using before comparing its answer with another.

Weight-to-power = weight / power, for example pounds per hp. Power-to-weight = power / weight, for example hp per pound or W/kg. They are reciprocals, so 10 lb per hp is 0.1 hp per pound. The calculator reports both forms.

Yes. Choose kW, W or PS as the power unit. One kilowatt is 1.341 mechanical hp, so 100 kW is 134.1 hp. The calculator converts to horsepower and watts and shows the ratio in every common unit. Choose kW as the power unit and the calculator converts it for you.

It does the same division for anything with a power and a weight, so yes. The typical values quoted on this page come from cars and motorcycles, though, so compare like with like. For aircraft and boats, check which power rating is quoted.

It does not estimate speed, quarter-mile times, torque or fuel economy. It divides the power you enter by the weight you enter, after any drivetrain loss and extra weight, and converts the units. Everything else depends on the vehicle. Use test data for those.

Enter the power and choose hp, PS, kW or W. Enter the weight and choose pounds or kilograms. Add any extra weight such as the driver, and a drivetrain loss if you want wheel power. The results show lb per hp, hp per lb, W per kg and more.