Watts per kg calculator
Enter your power in watts and your weight to get watts per kilogram, the figure that matters most on climbs. Add the bike weight to see the ratio for rider plus bike, and a target W/kg to see the power you would need.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Choose kilograms or pounds.
- Enter your power in watts and your weight.
- Optionally add the bike and kit weight, and a W/kg target.
How it works
W/kg is power ÷ weight in kilograms. If you enter pounds, the weight is converted using 1 lb = 0.45359237 kg. The target power is target W/kg × rider weight in kilograms.
Worked example
A rider produces 250 W and weighs 70 kg: 250 ÷ 70 = 3.57 W/kg. With an 8 kg bike and kit the total mass is 78 kg and 250 ÷ 78 = 3.21 W/kg. To reach 4 W/kg at 70 kg takes 4 × 70 = 280 W.
Notes
- Use the same power measure each time you compare riders or yourself over weeks.
- A power meter and a scale are the sources of error, so small differences are within the measurement noise.
Frequently asked questions
What is watts per kilogram?
Watts per kilogram, or W/kg, is a cyclist's power divided by body mass. On a steep climb most resistance comes from gravity, so a higher W/kg means faster climbing. On flat roads absolute power and aerodynamics matter more.
Which power should I use?
Any power you like: your functional threshold power (FTP) for a sustainable figure, or a five-minute or one-minute best for short efforts. The ratio is the same arithmetic. Compare like with like.
Should I include the bike?
Riders usually quote W/kg with rider weight only. Adding the bike and kit shows the ratio for the total mass moving uphill, which is what gravity acts on. Both numbers are given here.
How is the target power worked out?
It is the target W/kg multiplied by your rider weight. For example, 4 W/kg at 70 kg needs 280 W.