Watts per kilo (W/kg): understand and progress

On a bike, raw power (in watts) doesn't tell the whole story: it's the power-to-weight ratio, expressed in watts per kilo (W/kg), that best predicts performance, especially on climbs.

Why W/kg matters

On flat terrain, raw power and aerodynamics dominate. But as soon as it gets steep, you have to lift your own body weight: two cyclists at 250 W don't climb at the same speed if they weigh 60 and 80 kg. W/kg levels the playing field.

How to calculate it

Take your FTP (threshold power, in watts) divided by your weight in kg. Example: 240 W FTP for 75 kg = 3.2 W/kg. As a reference: ~2-3 W/kg for a recreational rider, 3-4 for a good amateur, 4-5+ for a seasoned competitor.

Two ways to improve it

• Increase power: threshold and sweet spot work plus VO2max training to raise your FTP.
• Optimize weight: losing excess fat improves the ratio — but never at the expense of health or power (see weight loss).

The biggest gains often come from power first: no need to starve yourself, it costs you watts.

Measure it seriously

A power meter (or a connected smart trainer) is necessary for reliable W/kg. Test your FTP every 6-8 weeks to track progress.

Progress methodically

Sports Coach AI programs the sessions that boost your FTP (and thus your W/kg) and tracks your power progress, managing load to help you improve without burning out. Especially useful for climbing better.