Centrifuge RPM to RCF Converter
Convert centrifuge speed between RPM and RCF (relative centrifugal force in g) from rotor radius.
Uses RCF = 1.118 × r × (RPM/1000)² for lab protocols.
Relative Centrifugal Force (RCF), also called g-force, is the actual force applied to a sample in a centrifuge. It depends on both the speed (RPM) and the rotor radius.
RPM to RCF formula:
RCF = 1.118 × 10⁻⁵ × r × RPM²
Where:
- RCF = relative centrifugal force (× g)
- r = rotor radius in centimeters (distance from center to sample)
- RPM = revolutions per minute
RCF to RPM formula (reverse):
RPM = √(RCF / (1.118 × 10⁻⁵ × r))
Why RCF matters more than RPM: Two centrifuges spinning at the same RPM will produce different g-forces if their rotors have different radii. RCF is the standardized way to report centrifugation conditions in scientific protocols.
Common centrifugation protocols:
| Application | RCF (× g) | Typical Time |
|---|---|---|
| Cell pelleting | 300–500 | 5–10 min |
| Blood separation | 1,500–3,000 | 10–15 min |
| Protein precipitation | 10,000–15,000 | 10–20 min |
| Microcentrifuge (general) | 12,000–16,000 | 1–5 min |
| Ultracentrifugation | 100,000+ | 1–4 hours |
| Bacterial pelleting | 3,000–6,000 | 10–15 min |
Common rotor radii:
- Microcentrifuge rotors: 6–8 cm
- Benchtop centrifuge rotors: 10–18 cm
- Floor-standing centrifuge rotors: 15–25 cm
- Ultracentrifuge rotors: 5–15 cm
Example calculation: For a rotor radius of 10 cm at 10,000 RPM: RCF = 1.118 × 10⁻⁵ × 10 × 10,000² = 11,180 × g
Tip: Always check your rotor’s maximum RPM rating. Exceeding it can cause catastrophic rotor failure. When following a protocol that specifies RCF, convert to RPM for your specific rotor using this calculator.
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