# How do I convert RPM to RCF?

Asked by ScottyMcGeester (1401) February 19th, 2013

I need to convert 3,000 RPM in a Beckman centrifuge to g (or also RCF). I’m a little confused as to how to do this exactly though, despite having found some equations. Supposedly it’s based on the radius of the rotor and then other stuff says it depends on the length between the rotor and the sample. But I’m confused as to how to measure it out. Do I measure out the length between the rotor and the edge of the sample, or the rotor and the REAR edge of the sample? I hope you understand what I mean.

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## 5 Answers

GQ. I have never tried this, but I’m guessing the center of the sample would give you the g on the entire sample.

@Adirondackwannabe Oh, duh. smacks forehead Physics. That makes sense.

@ScottyMcGeester I don’t know for sure that’s the right answer, but it sounds logical.

I also think that you should measure from the center of the centrifuge to the center of mass of the sample. The number of gs would be related to both this length and the RPM. I don’t know the exact equation involved, but I would be surprised if it weren’t calculated like this.

PhiNotPi (12611)

Here is a calculator that will do it for you.
Enter the RPM say 3600,
Enter the radius. say 120 mm
RCF = 1739 g
Done.

LuckyGuy (33523)

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