Power to Weight Ratio Calculator
A 70 kg cyclist holding 280 watts is riding at 4.0 W/kg, strong amateur racing form. This power to weight ratio calculator divides your power output by body or vehicle weight, reporting watts per kilogram for cycling and horsepower per tonne for cars. On any climb, this ratio decides who gets to the top first, not raw power.
Quick answer
Power to weight is simply power divided by mass: watts per kilogram or horsepower per tonne.
Power to weight
4.00 W/kg
hp per tonne
5.4
hp per 100 lb
0.24
What this tells you
- •Power to weight is simply power divided by mass: watts per kilogram or horsepower per tonne.
- •On flat ground raw power rules, but the steeper the hill, the more the ratio takes over.
- •Recreational cyclists hold 2 to 3 W/kg for an hour, strong amateurs 4, and Tour de France climbers above 6.
- •A hot hatch at 150 hp per tonne and a supercar at 500 live on the same scale.
How to Use
- 1Enter the power in watts (cycling) or horsepower (vehicles).
- 2Enter the weight in kilograms or pounds. For cycling, use body weight plus bike for full accuracy.
- 3Read the ratio in W/kg, hp per tonne, and hp per 100 lb.
- 4For cyclists, compare your hour-power (FTP) rather than a short sprint number.
How It Works
Formula
ratio = power / weightDivide watts by kilograms: 280 W / 70 kg = 4.0 W/kg. For vehicles, divide horsepower by weight in tonnes: a 1,400 kg car with 300 hp runs 214 hp per tonne. One horsepower is 745.7 watts, which is how the calculator bridges the two conventions.
Calculation note: values are processed in the order shown above, using the current input units.
Worked Examples
Amateur racing cyclist
Sustainable for an hour, this is competitive category 2 to 3 racing form.
Hot hatch
200 hp moving 1.3 tonnes, brisk but well short of sports car territory.
Sports car
The same math in imperial units, 500 hp against about 1.5 tonnes.
Cycling W/kg Benchmarks (1-hour power)
Typical sustainable power-to-weight levels by rider category.
| Rider | W/kg |
|---|---|
| New rider | 1.5 - 2.0 |
| Recreational | 2.0 - 3.0 |
| Trained amateur | 3.0 - 4.0 |
| Cat 1-2 racer | 4.0 - 5.0 |
| Domestic pro | 5.0 - 6.0 |
| World Tour climber | 6.0 - 7.0 |
Common mistakes
- Comparing a 5-second sprint W/kg with an hour benchmark. Duration changes the number completely, so match time frames.
- Forgetting the bike. Race bikes add 7 to 9 kg, which drops a 70 kg rider's real climbing ratio by about 10 percent.
- Using a car's curb weight without passengers and fuel. A driver and a full tank add 100 kg or more to the real figure.
- Chasing ratio through weight loss alone. Cutting weight below a healthy level costs more power than it saves grams.