P = (F_aero + F_roll + F_grav) · v
Your power meter already knows your CdA.
WattGap back-calculates the real aerodynamics of every bike you own from your own rides, then tells you which one is faster on your route, at your power.
Example · 22 mph, flat
Cervelo S5268W
CdA 0.253
Tarmac SL8296W
CdA 0.288
Zukas Ti307W
CdA 0.314
Δ 39W · S5 vs Zukas
01
Add your bikes
Pick a frame from the reference library: published wind-tunnel CdA, tire Crr at your PSI and rim width.
02
Drop your rides
.FIT, .GPX or .TCX, or a whole Garmin export. Historical wind is pulled for every ride.
03
Get your real CdA
Quality-gated back-calculation blends into the reference figure as your qualifying rides add up.