In this paper, the aerodynamically dissipated power loss in hard disk drives is studied. The effects of rotational speed and form factor on the dissipation power loss are analyzed and compared to experimental results using 3.5″, 2.5″ and 1″ disks. The torque coefficients for laminar and turbulent models are derived for various enclosure conditions. We implement experiments using a vacuum chamber and calculate frictional power loss by disk rotation. For a 1-inch disk, the power dissipation agrees well with the laminar model, which is inversely proportional to the half power of Reynolds number. The frictional power consumption by 3.5-inch disk is similar to the air turbulent model. Finally, we propose the drive enclosure geometry to minimize the aerodynamic power loss based on the experimental results.