RCF ↔ RPM Converter
Convert centrifuge speed between RPM and relative centrifugal force using the standard radius-based RCF formula.
Convert RCF and RPM
Convert centrifuge speed between RPM and relative centrifugal force using rotor radius.
How the RCF ↔ RPM Converter works
Thermo Fisher gives the conversion RCF = 1.118 × 10⁻⁵ × radius(cm) × RPM². Rearranging allows RPM to be calculated from RCF when rotor radius is known. Because force scales with the square of RPM and linearly with radius, the same RPM does not mean the same g-force in different rotors.
How to use this rcf ↔ rpm converter
Choose the conversion direction, enter RPM or RCF and enter rotor radius in centimetres. Use the radius definition appropriate to your protocol and centrifuge—often distance from the axis of rotation to the sample position of interest. Check the rotor manual when maximum, average or minimum radius matters.
How to interpret the result
RCF is generally more transferable between centrifuges because it describes force relative to gravity rather than motor speed alone. The optional rotor-tip speed is shown only as geometric context; it is not a substitute for RCF and should not be used to exceed a rotor’s mechanical rating.
Assumptions and limitations
Rotor geometry, sample position and manufacturer limits still matter. Never calculate an RPM that exceeds the certified rotor/centrifuge maximum. Some protocols depend on k-factor, sedimentation path or time in addition to RCF. This calculator does not assess rotor compatibility, balancing or centrifuge safety.
Practical example and workflow
At 5,000 RPM and a 10 cm radius, RCF is about 2,795×g. If the same 5,000 RPM is used in a 5 cm rotor, force is roughly half, showing why copying RPM between different rotor geometries can change a protocol materially.