What Is W/kg and Why It Matters
Watts per kilogram (W/kg) is the single most useful number for comparing cycling ability across riders of different sizes. Two riders can have very different absolute FTP values -- say 200 W and 300 W -- but if their W/kg is similar, they will climb at roughly the same speed.
The formula is simple: divide your FTP in watts by your body weight in kilograms. If you weigh 75 kg with a 250 W FTP, your W/kg is 3.33.
Formula
W/kg = FTP (watts) / Body weight (kg)
Example: 250 W / 75 kg = 3.33 W/kg
How to Improve Your W/kg
There are two levers: increase FTP or reduce body weight. For most riders, the higher-return approach is to focus on structured training that raises FTP, rather than aggressive weight loss that can compromise power output and recovery.
- Use power zone training to systematically raise your threshold.
- Include 2-3 sessions per week at or near threshold intensity, with adequate recovery between efforts.
- Track W/kg over months, not days. Short-term weight fluctuations (hydration, meals) can swing the number by 0.1-0.2 W/kg without any fitness change.