Power-to-weight ratio calculator
Power alone does not compare cars fairly, because a lighter car needs less power for the same pace. Enter power and weight.
Loading the tool…
Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter power, power unit and weight.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
hp per tonne = hp ÷ (weight in kg ÷ 1000). kg per hp = weight ÷ hp. W per kg = power in watts ÷ weight, where 1 hp = 745.7 W.
Example
Inputs: Power = 300, Power unit = hp, Weight = 1,500 kg. Result: hp per tonne: 200 hp/t; kg per hp: 5 kg/hp; Watts per kg: 149.1 W/kg.
Limits and caveats
- Official weights may exclude driver and fuel; add them for a real-world figure.
- The ratio is a performance indicator only; traction, gearing and tires also affect acceleration.
Questions about this tool
Which figure should I compare?
Higher hp per tonne means relatively stronger; lower kg per hp means the same. They are two views of one comparison.
Should I use curb or gross weight?
Use the same kind of weight for every car you compare; curb weight plus driver is usually the clearest.
What does a typical family car score?
A 150 hp sedan weighing 1300 kg gives about 115 hp per tonne.