How to use
- 1Enter your FTP in watts, your weight and sex to see W/kg and your level.
- 2Read your seven Coggan power zones in watts from the zone table.
- 3In the estimator, enter speed, gradient, rider and bike weight, position, surface and headwind.
- 4See the total power and how it splits into air drag, rolling resistance and climbing.
W/kg and the Allen & Coggan levels
Watts per kilo is FTP (the power you can hold for about an hour) divided by body weight; it decides how fast you climb. The level table follows Hunter Allen and Andrew Coggan, Training and Racing with a Power Meter (2010), as used in current Garmin devices: for men Untrained is below 2.23 W/kg, Fair 2.23–2.78, Good 2.79–3.92, Excellent 3.93–5.04 and Superior 5.05 and up; for women the cut-offs are 1.90, 2.36, 3.33 and 4.30. A 75 kg man with a 250 W FTP rides at 3.33 W/kg — Good; a woman with the same figure would rate Excellent.
Coggan’s seven power zones
Zone 1 active recovery is below 55% of FTP, Zone 2 endurance 56–75%, Zone 3 tempo 76–90%, Zone 4 threshold 91–105%, Zone 5 VO2max 106–120%, Zone 6 anaerobic capacity 121–150% and Zone 7 neuromuscular power above 150% (sprints of a few seconds). Most base training sits in Zone 2; classic threshold sessions are 2 × 20 minutes in Zone 4. Retest FTP every 6–8 weeks, for example with a 20-minute test × 0.95.
How the power estimate works
The estimator adds three forces and multiplies by speed: air drag (½ × air density 1.225 kg/m³ × CdA × air speed²), rolling resistance (Crr × total mass × g) and gravity on the gradient (mass × g × sin of the slope angle), then adds 2.4% drivetrain loss. On the hoods (CdA 0.34) with 84 kg total, 30 km/h on the flat needs about 150 W — 80% of it air drag — while 15 km/h up an 8% climb needs about 310 W, almost all of it gravity. Real power meters will differ with wind, tyre pressure and road surface.
Frequently asked questions
What is a good watts per kg?
By the Allen & Coggan scale, 2.8–3.9 W/kg FTP is Good for men and 2.4–3.3 for women; club racers are often around 3.5–4.5, and professional riders exceed 5.5–6 W/kg.
How do I calculate my FTP zones?
Multiply your FTP by Coggan’s percentages. With a 250 W FTP, Zone 2 is 140–188 W, Zone 4 is 228–263 W and Zone 5 is 265–300 W. The table does this automatically.
How many watts do I need to ride at 30 km/h?
On flat roads with no wind, about 130–170 W for a typical road rider on the hoods, depending on position, weight and tyres. Every extra 5 km/h needs a lot more, because air drag grows with the cube of speed.
What does CdA mean?
CdA is the drag coefficient times frontal area, in m². An upright position is around 0.40–0.45, the hoods about 0.32–0.36, the drops about 0.30, and an aero time-trial position 0.20–0.25.
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