How do we determine our centrifuge RCF? In centrifugation RCF is dependent upon the RPM but it is also dependent on the radius of the rotor from the axis to the bottom of the centrifuge tube. From the figure at left we see that the formula RCF = 1.118 x 10-5 x r x N2 will let us calculate the RCF from the radius of the particular rotor we are using and the RPM we are spinning.
Be careful when purchasing a centrifuge based on a maximum RCF. There may be only one rotor available for that centrifuge which will achieve the maximum RCF and it may not be the rotor you need. Rotor information is available from most manufacturer’s websites. When purchasing a centrifuge be sure to check the max. RCF of the rotor you intend to use. In other words, work backwards. Choose the rotor first.