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Power to Speed (indoor to outdoor)
Indoor speed doesn't convert; power does. Enter watts and we estimate flat-road speed.
Estimated outdoor speed (km/h)—
Pace · per km—
Physics model (Martin et al.). No wind, sea level. Typical CdA 0.30 to 0.40 (road). Mass in kg (body + bike).
Why doesn't indoor speed convert directly to outdoor speed?
Indoor trainers use resistance models that don't match real-world aerodynamic and rolling resistance — power is the common unit that does.
What CdA should I use?
Typical road position CdA is 0.30 to 0.40 m²; a more aggressive aero position lowers it further.