01 · Inputs
Where do your watts come from?
Pick the honest one. Nobody is watching.
1. A typical week looks like…
2. Sporting background?
3. Four flights of stairs?
4. Twenty minutes hard on a bicycle sounds…
Fair warning: estimate mode is a party trick with a physics degree. It maps your answers to a plausible W/kg band - it is not a lab test, and the real answer needs a power meter and twenty uncomfortable minutes.
Fiddle with the machinery (bike, position, gradient)
8.1%
Your VAM · the number that matters
– m/h vertical
Watts per kilo
–
FTP
–
Classification
–
Coggan-style ladder below
Flat speed
–
same watts, 0% gradient
Fuel bill
–
Alpe d'Huez
–
your full-climb time
The Alpe d'Huez test
13.8 km at 8.1%, 21 hairpins, 1,120 m of climbing. You and a Tadej Pogačar modelled at 7.0 W/kg start together. He does not wait.
| When you reach… | Pogačar's lead | Where is he then? |
|---|
Reverse gear: speed to watts
Tell the machine a flat-road speed and it tells you what it costs.
km/h needs– watts
02 · Method
Every assumption, on the table.
The model is a steady-state power balance, the standard way cycling speed is estimated.
The physics
power at the wheel = v · m · g · (grade + Crr) + ½ · ρ · CdA · v³
- We solve for speed v given your watts; 3% drivetrain loss, air density ρ = 1.225 kg/m³, rolling resistance Crr = 0.004 (decent road tyres).
- Climbing speed uses your chosen gradient; flat speed uses the same watts at 0%. Reverse mode flips the equation: speed in, watts out.
- VAM (velocità ascensionale media) is climbing speed converted to vertical metres per hour - the number Italian TV obsesses over, and the honest currency of a climb.
- No wind, no drafting, no altitude penalty, steady pacing. Real roads are ruder.
- The Pogačar reference: 66 kg at 7.0 W/kg (462 W), riding the drops. That figure comes from Velo's analysis of his 39'30" ascent of Plateau de Beille at the 2024 Tour - about 455 W, roughly 7 W/kg.
- Estimate mode maps quiz answers onto the W/kg bands below. It is deliberately generous fun, clearly labelled as an estimate.
The sources
- Power-to-weight ladder: the Coggan-style FTP bands from Training and Racing with a Power Meter (Allen & Coggan), as published in this W/kg chart.
- Alpe d'Huez - 13.8 km, 8.1% average, 21 hairpins, 1,120 m of elevation: Cycling Weekly.
- The record: Marco Pantani, 37'35" in 1997 - timed over the old 14.5 km route (The Athletic). Over the modern 13.8 km route his 1997 ride works out to 36'55", and his fastest ever on that route is 36'50" from 1995 (record history).
- Pogačar at ~7 W/kg for 39 minutes: Velo power analysis, 2024 Tour de France.
- FTP = 95% of 20-minute power: the Allen & Coggan protocol, explained by Favero.
- Calories: kilojoules of pedal work ≈ food calories burned, because human engines run at roughly 20-25% efficiency - the TrainerRoad rule of thumb.
- Donut exchange rate: 190 kcal per Krispy Kreme Original Glazed.