In centrifugation the clearing factor or k factor represents the relative pelleting efficiency of a given centrifuge rotor at maximum rotation speed. It can be used to estimate the time (in hours) required for sedimentation of a fraction with a known sedimentation coefficient (in svedbergs):
The value of the clearing factor depends on the maximum angular velocity of a centrifuge (in rad/s) and the minimum and maximum radius of the rotor:
As the rotational speed of a centrifuge is usually specified in RPM, the following formula is often used for convenience:
Centrifuge manufacturers usually specify the minimum, maximum and average radius of a rotor, as well as the factor of a centrifuge-rotor combination.
For runs with a rotational speed lower than the maximum rotor-speed, the factor has to be adjusted: