Watts per kg Calculator
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Watts per kilogram (W/kg) is your power divided by body weight. On climbs, gravity resists your total mass, so W/kg matters more than raw watts: 250 W at 70 kg is 3.57 W/kg.
| Watts per kilogram | 3.571 W/kg |
| Watts per pound | 1.62 W/lb |
| With bike (total 78 kg) | 3.205 W/kg |
| Power needed for a target | |
| 2.5 W/kg | 175 W, or lose no weight at your current power |
| 3 W/kg | 210 W, or lose no weight at your current power |
| 3.5 W/kg | 245 W, or lose no weight at your current power |
| 4 W/kg | 280 W, or lose 7.5 kg at your current power |
| 4.5 W/kg | 315 W, or lose 14.4 kg at your current power |
| 5 W/kg | 350 W, or lose 20 kg at your current power |
Show steps
- W/kg = power ÷ body weight = 250 ÷ 70 = 3.571.
- On a climb, gravity resists total mass (rider + bike), so the system ratio uses both.
The formula
W/kg = power (W) ÷ body weight (kg). Including the bike: W ÷ (rider + bike). To reach a target, power needed = target × weight, or the weight that gives the target = power ÷ target.
Why it matters on climbs
On a steep hill most of your power lifts mass against gravity, so speed is close to proportional to W/kg. On flat roads air resistance dominates and raw watts and aerodynamics matter more.
Improving W/kg
Raise power with structured training or reduce weight carefully; losing muscle lowers power too, so focus on training and nutrition rather than crash diets.
Watts per kg Calculator quiz: 10 questions
Test yourself with 10 multiple-choice questions. Choose an answer and press Submit to see if you are right and why. Your score appears at the end.
Quiz complete
Frequently asked questions
What is a good W/kg?
Many recreational cyclists are 2 to 3.5 W/kg at FTP; professional climbers exceed 6.
Should I include bike weight?
For climbing speed, yes: the calculator shows both.
Which power should I use?
Usually FTP, but you can enter any duration.
Does W/kg matter in time trials?
Less on flat courses, where aerodynamics matter more.
Can I use pounds?
Yes, switch the weight units.
Sources
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