Frontal area is the total frontal area presented by the rider and bike. A typical cyclist presents a frontal area of 0.3 to 0.6 meters squared depending on position. Frontal areas of an average cyclist riding in different positions are as follows.

Tops 0.632
Hoods 0.40
Drops 0.32

Aerodynamic drag: CdA is calculated by multiplying Frontal Area: A by the Coefficient of drag: Cd.