GEARING personalized gearing calculator

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Compare setups

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Cadence lanes

each gear's cadence across grade at your FTP — click the plot above to set the effort

Climbing ceiling

steepest grade you can climb at your minimum cadence in the easiest gear, vs power. Below the line you keep cadence; above it you're grinding.

+ adds a tab that clones this setup — tweak one thing, then press 1–9 to flash between them. Click the plot to pin a cross-section (Esc clears). Steady-state physics model: gravity + rolling resistance + fixed-CdA aero.

CdA — aerodynamic drag area

CdA (drag coefficient × frontal area, m²) is your whole-system aero — rider + bike. It's the biggest lever on flat and descending speed: the power to fight drag rises with the cube of speed.

Typical values for a fit road rider (bigger riders sit higher):

PositionCdA (m²)
Upright / on the tops0.40–0.45
Hoods — everyday road0.30–0.36
Drops0.27–0.32
Aggressive low drops0.25–0.28
Descending tuck0.22–0.25
TT / aero bars0.20–0.26
Sprint — out of saddle0.30–0.36
Gravel — bags, wide tyres0.35–0.42
MTB — flat bar0.40–0.48

Measure your own with a power meter — no wind tunnel needed:

Crr — rolling resistance

Crr (coefficient of rolling resistance, dimensionless) is how much your tyres drag on the road. Resistance = Crr × system weight, so it dominates at low speed and on climbs — where aero barely matters. Lower is faster.

Ballpark values (decent tyre, sensible pressure):

Surface / tyreCrr
Fast tubeless race, smooth road0.003–0.004
Good clincher, training0.004–0.006
Rough / chipseal road0.006–0.008
Gravel tyre on dirt/gravel0.008–0.013
MTB knobbly on trail0.012–0.020

Tyre and pressure matter a lot — on rough ground, lower pressure can be faster (less bouncing). Lab-tested numbers per tyre:

FTP — functional threshold power

FTP is the highest power (watts) you can hold in a quasi-steady state for roughly an hour — your aerobic ceiling, and the usual anchor for training zones.

Here it scales your power zones (Z2–Z5) and the plot's power band, so getting it roughly right matters more than exactly right.

Estimate it:

TestFTP ≈
20-min all-outavg × 0.95
Ramp test~75% of last min
Best ~1 hr effortaverage power

For context: recreational ≈ 2–3 W/kg, keen amateur ≈ 3–4, elite 5+ W/kg.