Transfer Time: 

The transfer time to or from the disk depends on the rotational speed of the disk and it is estimated as
                                  

where
                                 Transfer time
                                   Number of bytes to be transferred.
                                 Numbers of bytes on a track
                                  Rotational speed, in revolution per second.

Thus,

the total average access time can be expressed as
                                     
where    is the average seek time.