Cycling Power in Watts

Cycling power: watts, FTP and W/kg

Cycling power measures the mechanical work you produce at the pedals: P = F · v = T · ω. That is force times speed at the wheel, or torque times angular velocity at the crank, and either way the answer comes out in watts. Going uphill, gravity does most of the work: P_grav ≈ m · g · v · sin(slope). Example: a 75 kg rider at 25 km/h on a 2% grade needs roughly 200-220 W once you add in aero and rolling resistance. The FTP (Functional Threshold Power) is the highest power you can hold for about an hour. The Coggan protocol estimates it as ≈ 95% × the average power of a 20-minute all-out test. The W/kg ratio levels the field across body sizes: Tadej Pogacar holds around 6.4 W/kg on 30-minute climbs, while a recreational rider sits closer to 2.5-3 W/kg.

Applications: training, racing and indoor cycling

Power data is what runs indoor sessions on Zwift, TrainerRoad and Rouvy, where a smart trainer reads your watts in real time. Wahoo Elemnt and Garmin Edge head units show power zones (Coggan Z1-Z7) and keep track of TSS/IF for periodization. Strava normalizes its segment leaderboards by W/kg, while Bkool and Sufferfest build workouts around %FTP. A typical plan puts intervals at 88-94% FTP for sweet spot, 95-105% for threshold, and 106-120% for VO2max.

FAQ

Do I need a power meter to use this? A power meter (Stages, Quarq, Favero) or a smart trainer gives you the real number. Without one, you can still estimate from speed, grade and weight, just keep in mind that wind and road surface throw the figure off.

Why 95% of the 20-min test? Coggan's data showed that athletes can hold roughly 95% of their 20-minute power across a full hour. Some riders prefer the ramp test, or the newer lab-style protocols from Karoo/INSCYD.

How often should I retest FTP? Roughly every 6-8 weeks while you are training in a structured block. When the numbers stop moving, that is the signal to reset your zones.

Is W/kg the only metric that matters? Not really. On flat time trials, raw watts and aerodynamics decide the result. W/kg only takes over on the long climbs.