# Power-to-Weight Ratio Calculator

URL: https://speedycalculator.com/calculators/physics/power-to-weight-ratio/
Last updated: 2026-10-30

> The power-to-weight ratio calculator divides power by mass to compare the performance of cars, motorcycles, aircraft and cyclists, in W/kg, hp per tonne and kg per hp.

## Inputs

- Power (hp, kW, W, PS)
- Weight (kg, g, mg, t, lb, oz)

## Results

- Power-to-weight ratio
- Horsepower per tonne
- Weight per horsepower
- Pounds per horsepower

## Formula

```
PWR = P / m
```

## Explanation

Power-to-weight ratio is the single best predictor of acceleration and climbing ability. A cyclist producing 4 W/kg climbs faster than a heavier rider with more watts; a light sports car can outrun a more powerful but heavier one.

### How to use the Power-to-Weight Ratio Calculator

- **Power**
- **Weight**

Results update as you type, every field has its own unit menu, and everything is calculated in your browser.

### How it works

Enter the power and the mass (including driver or rider). The ratio is given in several common forms.

### Inputs explained

FieldWhat to enterPowerUnits: hp, kW, W, PSWeightUnits: kg, g, mg, t, lb, oz

### What each result means

- **Power-to-weight ratio** = [Power]÷[Weight]
- **Horsepower per tonne** = [Power]÷745.69987158227÷([Weight]÷1000)
- **Weight per horsepower** = [Weight]÷([Power]÷745.69987158227)
- **Pounds per horsepower** = [Weight]÷0.45359237÷([Power]÷745.69987158227)

### Example values

How the main result changes when **Power** changes and everything else stays at the example values above:

Power (hp)Power-to-weight ratio (W/kg)15079.896225119.845300159.793375199.741450239.689600319.586

## Worked example

Inputs — Power: 300 hp; Weight: 1,400 kg.

Results — **Power-to-weight ratio = 159.793 W/kg**; Horsepower per tonne = 214.29 hp/t; Weight per horsepower = 4.667 kg/hp; Pounds per horsepower = 10.288 lb/hp.

## Key terms

- **Power-to-weight ratio**: Power divided by mass.

## FAQ

**What is a good power-to-weight ratio for a car?**
Family cars: 50–100 hp/t; sports cars: 200–400 hp/t; hypercars: over 600 hp/t.

**What W/kg do cyclists produce?**
Amateurs 2–3 W/kg for an hour; professionals 5.5–6.5 W/kg.

**Is a higher ratio always better?**
For acceleration yes, but traction and aerodynamics also matter.

**Should I include the driver?**
Yes – the mass actually being accelerated.


## Sources

- [OpenStax – University Physics Volume 1](https://openstax.org/details/books/university-physics-volume-1)
- [HyperPhysics (Georgia State University)](http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html)