Convert G-Force (RCF) to RPM for Lab Centrifuges | BT Lab Systems

Benchtop centrifuges are typically sold with their speed settings as revolutions per minute (rpm), however many experimental procedures have precise centrifugation conditions specified in terms of relative centrifugal force expressed in unites of gravity (times gravity or x g).  The following formula is for the conversion between Relative Centrifugal Force (RCF) and RPM:

g = (1.118 x 10^-5) x R x S²

Where g is the relative centrifugal force , R is the radius of the rotor in centimeteres and S is the speed of the centrifuge in revolutions per minute (RPM). The follow table is a simple reference for common rotor sizes and their RCF values in units of times gravity (x g).  For example, an experiment requires a sample to centrifuged at 5,000g and the centrifuge that is available has a rotor of 9cm, using the table below, the centrifuge needs to be run at a speed of 7,000rpm as this gives an RCF of 4930 x g.  Using the formula the precise speed would be 7,049rpm.