---
title: Relative centrifugal force (RCF)
url: https://regenmedtools.com/glossary/rcf/
type: glossary
primaryQuery: relative centrifugal force
---

# Relative centrifugal force (RCF)

RCF is the force a centrifuge applies to a sample, expressed as a multiple of Earth's gravity and written as g. It is what a spin protocol specifies. RCF depends on both rotor speed and rotor radius, so the same RPM produces different RCF in different machines.

RCF is calculated as 1.118 x 10⁻⁵ x r x N², where r is the rotor radius in centimetres and N is speed in RPM. Some manuals write it as 11.18 x r x (N/1000)², which is the same relation. Because force grows with distance from the axis, there is no single RCF in a tube: papers distinguish RCF-max, RCF-min, RCF-average, and RCF at the clot.


## Related
- [rpm](https://regenmedtools.com/glossary/rpm/)
- [r-max](https://regenmedtools.com/glossary/r-max/)
- [sedimentation](https://regenmedtools.com/glossary/sedimentation/)