Centrifugal G Force Calculator
Convert between RPM and RCF (g-force)
Understanding Centrifugal Force
This calculator helps you determine the relationship between three key variables in centrifugation: Relative Centrifugal Force (RCF), also known as g-force, Revolutions Per Minute (RPM), and the Rotor Radius. Correctly setting these parameters is crucial for successful sample separation and to ensure you are following a specific protocol.
What is RCF (g-force)?
RCF is the force exerted on the contents of the rotor, calculated relative to the Earth’s gravitational force. It is the most accurate and reproducible parameter for centrifugation because it is independent of the specific centrifuge and rotor used. Protocols should ideally specify the required RCF (e.g., 1000 xg).
What is RPM?
RPM is a measure of the speed of the rotor, indicating how many full rotations it completes in one minute. While easy to set on a centrifuge, the g-force produced at a specific RPM will vary depending on the size (radius) of the rotor. A larger rotor will generate a higher g-force than a smaller rotor at the same RPM.
How to Use the Calculator
- To find RCF: Enter the RPM and Rotor Radius, then click “Calculate”.
- To find RPM: Enter the RCF (g-force) and Rotor Radius, then click “Calculate”.
- To find Radius: Enter the RCF and RPM, then click “Calculate”.
The calculator will automatically determine the missing value. Ensure you select the correct unit for your radius measurement.
Frequently Asked Questions (FAQs)
Why should I use RCF instead of RPM?
RCF is a standardized value. Using RCF ensures that your results are consistent and reproducible, even if you switch to a different centrifuge with a different rotor size. An RPM setting alone does not guarantee the same force is applied across different machines.
How do I measure the rotor radius?
Measure the distance from the center of the centrifuge spindle to the bottom of the sample tube when it’s in the rotor. For swinging-bucket rotors, measure with the bucket in its horizontal (spinning) position. Always consult your centrifuge manual for the most accurate radius measurement.
What’s the formula to convert RPM to RCF?
The standard formula is: RCF = 1.118 × 10-5 × r × (RPM)2, where ‘r’ is the radius in centimeters. Our calculator handles the unit conversions for you automatically.
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