Watts / kg & Climb Time Predictor

How to use this calculator

1. Set your honest FTP. Either from a recent 20-minute test (×0.95) or a ramp test. If your last test is older than 8 weeks, the result is optimistic.
2. Pick the duration that matches your climb. A 4-minute kicker is not an FTP effort. A 60-minute climb is. Pick the value closest to what you expect to spend on the climb.
3. Add wind and altitude if they're real. A 25 km/h headwind at 8% adds the equivalent of another full percentage point of gradient. Altitude above 2000 m starts costing 1-2% power per 500 m.
4. Compare to your last attempt. The point isn't the absolute number — it's whether the model agrees with what you actually did.

What this calculator does differently

Online W/kg calculators usually give you the number and stop. The climb-time table is the second thing most riders actually want — and most public versions either skip it entirely or use the wrong formula (often implying you'd climb Alpe d'Huez at 30 km/h).

What we add that other versions usually don't:

• Duration-aware power. Not just FTP — your 5-minute power is ~1.4× FTP, your 60-minute power is exactly FTP, your 2-hour power is ~0.88×. The climb speed reflects the chosen duration.
• Aero drag at climbing speed. We don't assume a flat-road CdA — climbing speed is slower, so the relative weight of aerodynamic drag is small but non-zero, especially with a headwind.
• Altitude correction. A simple Peronnet-style model: power drops ~7% at 3000 m, ~10% at 4000 m. Choose honestly.
• VAM across three durations. Because the climb profile matters — short ramps, mid-length climbs, and hour-long ascents are three different efforts.

Reading the results

W/kg categories are based on Coggan's original training levels, with "Cat 5" (untrained) added for context:

• Cat 5: < 2.0 W/kg — recreational / new to structured training
• Cat 4: 2.0 – 2.9 — club / sport recreational
• Cat 3: 3.0 – 3.9 — regular racer
• Cat 2: 4.0 – 4.9 — elite amateur / domestic pro
• Cat 1: 5.0 – 5.9 — WorldTour domestique level
• HC: 6.0+ — GC contender level

VAM is the rate of vertical ascent in meters per hour. To estimate climb time: climb_time_minutes = (vertical_meters / VAM) × 60. So at 1500 VAM a 600 m climb takes 24 minutes.

Common questions

My predicted climb time is faster than what I actually do. Why?

Three usual culprits: (1) FTP is too high — most riders over-estimate by 5–10%; (2) the climb is harder than the chosen duration — a 60-minute effort for a 90-minute climb is wrong; (3) nutrition or pacing — if you fade in the last third, your FTP isn't the limiting number.

Does bike weight matter?

For climbs, total system weight (you + bike + water + kit) matters. We've used your body weight — add 8–9 kg for a road bike, 10–12 kg for a gravel bike, 15+ kg for a loaded touring rig.

What about e-bikes?

The motor adds up to 250 W of assist, but this calculator assumes human-only power. If you ride e-MTB, use the FTP that includes your expected contribution only, not the motor.

Is W/kg the only number that matters?

No. On a flat TT, absolute watts matter more because aero drag dominates. W/kg is climbing-specific. The aero calculator on this site covers the flat-road case.

Why does altitude drop my predicted speed so much?

Thinner air means less oxygen delivery per breath. Most trained riders lose 6–8% of sustainable power at 2500 m and 10–14% at 3500 m. The numbers here use the Peronnet & Massicotte model.