Centrifuge RPM to RCF Converter
Convert between RPM and RCF (g-force) for centrifuges.
Enter rotor radius and speed for bidirectional conversion.
RCF (Relative Centrifugal Force) is the force exerted on a sample in a centrifuge, expressed as multiples of Earth’s gravitational acceleration (× g). RPM (Revolutions Per Minute) is the rotational speed of the centrifuge rotor.
Scientists and lab protocols specify centrifugation in RCF (× g) because it is independent of the rotor being used. However, most centrifuges display speed in RPM. This converter translates between the two.
Formulas:
RPM to RCF:
RCF = 1.118 × 10⁻⁵ × r × RPM²
RCF to RPM:
RPM = √(RCF / (1.118 × 10⁻⁵ × r))
Where:
- RCF = Relative centrifugal force (× g)
- RPM = Revolutions per minute
- r = Rotor radius in centimeters (distance from center of rotation to the sample)
How to measure rotor radius: The radius (r) is the distance from the center of the rotor to the bottom of the sample tube when it is in the centrifuge. This is sometimes called the “maximum radius” and is listed in the rotor specifications from the manufacturer.
Worked Example (RPM to RCF): Centrifuge spinning at 10,000 RPM with a rotor radius of 10 cm: RCF = 1.118 × 10⁻⁵ × 10 × 10,000² = 1.118 × 10⁻⁵ × 10 × 100,000,000 = 11,180 × g
Worked Example (RCF to RPM): Protocol requires 3,000 × g with a rotor radius of 15 cm: RPM = √(3,000 / (1.118 × 10⁻⁵ × 15)) = √(3,000 / 0.0001677) = √17,889,088 ≈ 4,230 RPM
Common centrifuge protocols:
| Application | Typical RCF | Duration |
|---|---|---|
| Pellet cells (blood) | 300 – 500 × g | 5 – 10 min |
| Pellet bacteria | 3,000 – 5,000 × g | 10 – 15 min |
| Pellet cell debris | 10,000 – 15,000 × g | 10 – 20 min |
| Pellet microsomes | 100,000 × g | 60 min |
| DNA precipitation | 12,000 – 16,000 × g | 10 – 15 min |
| Protein pellet | 15,000 – 20,000 × g | 15 – 30 min |
Common rotor radii:
| Rotor Type | Typical Radius |
|---|---|
| Microcentrifuge | 6 – 8 cm |
| Tabletop clinical | 10 – 15 cm |
| Floor-standing | 15 – 25 cm |
| Ultracentrifuge | 6 – 10 cm |
Important notes:
- Always match the RCF from the protocol, not the RPM, when using a different rotor.
- Using the wrong radius can result in under- or over-centrifugation, affecting experimental results.
- Some rotors list both minimum and maximum radius — use the maximum radius for the strongest force at the tube bottom.