Power-to-Weight Ratio Calculator

Quickly compare engine output to vehicle weight in hp/lb, kW/kg, and hp/kg.

Engine Power

Enter engine output in your preferred power unit.

Vehicle Weight

Enter curb weight or race weight including driver.

Calculated Ratios

Enter power and weight to see results.

How the power-to-weight ratio calculator works

This calculator takes any supported power and weight units, converts them to common base units, and then computes three standard performance ratios. Power is first converted to watts, and weight is converted to kilograms. From there, watts are converted to horsepower (hp) and kilowatts (kW), while kilograms can be converted to pounds (lb) for the hp/lb output.

Under the hood, each unit has a fixed conversion factor (for example, 1 kW = 1000 W and 1 lb ≈ 0.45359237 kg). The tool multiplies your inputs by these factors to reach watts and kilograms, then divides power by weight to get: hp / lb , kW / kg and hp / kg. Only the display is rounded based on your Decimals setting — the internal calculation keeps full precision.

How to use this calculator

Enter the engine output in the Engine Power field and choose the appropriate unit (hp, kW, W, etc.).
Enter the vehicle mass in the Vehicle Weight field and select the weight unit (lb, kg, tons, etc.).
As soon as both values are valid, the calculator instantly updates the three ratios: hp per pound, kW per kilogram, and hp per kilogram.
If needed, adjust the Decimals to see more or fewer digits in the results without changing the underlying precision.

Notes and tips

Use curb or race weight that includes the driver, fuel, and typical setup — this gives more realistic power-to-weight ratios.
Higher power-to-weight generally means stronger acceleration, but gearing, traction, and aerodynamics also affect real-world performance.
You can safely mix any supported power and weight units — the tool always normalizes to watts and kilograms before calculating ratios.

Common examples of Power-to-Weight Ratio

Vehicle type	Example	Power (hp)	Weight (kg)	Power-to-weight (hp/kg)	Power-to-weight (hp/ton)
Everyday compact car	1.6L family hatchback	120	1300	0.092	92
Mid-size sedan	2.0L petrol sedan	180	1500	0.12	120
Hot hatch	Turbo hatchback	250	1400	0.179	179
Sports car	RWD coupe	350	1450	0.241	241
Supercar	High-end V8/V10	600	1400	0.429	429
Superbike	1000cc sport bike	200	200	1	1000
Electric SUV	Dual-motor EV	400	2200	0.182	182
Heavy truck	Loaded tractor-trailer	450	18000	0.025	25

Frequently Asked Questions

What is the Power to Weight Ratio?

Power-to-weight ratio is a measure of how much power is available to move each unit of weight. It compares an engine’s output (in horsepower or kilowatts) to the mass of the vehicle (in kilograms, pounds, or tons) and is usually written as hp/kg, hp/lb, kW/kg, or kW/ton.

How to calculate the Power to Weight ratio?

To calculate power-to-weight ratio, divide the engine power by the vehicle weight using consistent units. For example, in hp per kilogram: Power-to-weight ratio = Engine power (hp) ÷ Vehicle weight (kg). You can do the same with kW/kg, hp/lb, or kW/ton as long as you keep the units matched.

How is Power to Weight ratio it useful?

Power-to-weight ratio is useful because it gives a quick, comparable way to judge how strong a vehicle’s acceleration and performance can be. A higher ratio usually means faster acceleration, better overtaking ability, and a more responsive feel, even if total power or weight alone doesn’t look impressive.

How do I convert the Power to Weight Ratio to different units?

To convert a power-to-weight ratio between units, convert the power and weight separately and then recompute the ratio. For example, to go from hp/kg to hp/lb, convert the weight from kilograms to pounds and divide the same power by the new weight. A calculator like this one automates those conversions internally so you only need to pick your preferred units.

What are some practical applications of the Power to Weight Ratio?

Power-to-weight ratio is widely used in motorsport, car and motorcycle tuning, aviation, marine design, and performance comparisons. It helps racers compare builds, manufacturers benchmark different models, and buyers understand why a lighter car with less power can still feel quicker than a heavier car with more power.

Can this calculator be used for different types of vehicles?

Yes. You can use a power-to-weight ratio calculator for cars, motorcycles, trucks, buses, karts, boats, and even aircraft. As long as you know the engine power and the total weight, the same formula applies—the labels change, but the physics stays the same.

Real World example of calculating the Power to Weight ratio

Imagine a car with 300 hp that weighs 1500 kg. The power-to-weight ratio in hp/kg is 300 ÷ 1500 = 0.20 hp/kg. In hp per metric ton, that is 200 hp/ton because 1500 kg is 1.5 tons (300 ÷ 1.5 = 200). If the car instead weighs 3300 lb, the ratio in hp/lb is 300 ÷ 3300 ≈ 0.091 hp/lb.