G-Force RPM Calculator

Convert between relative centrifugal force (RCF/g) and revolutions per minute (RPM) for centrifuge settings

cm
RPM
Relative Centrifugal Force 2,839 × g
RCF (× g) = 1.118 × 10⁻⁵ × r × (RPM)²
RPM = √[RCF / (1.118 × 10⁻⁵ × r)]
where r = rotor radius in cm

What is RCF/G-Force?

Relative Centrifugal Force (RCF) or G-force is the acceleration applied to samples during centrifugation, expressed as multiples of Earth's gravity (g). It depends on both the rotor speed (RPM) and the radius from the center of rotation.

Rotor Radius Measurement

Measure from the center of the rotor to the bottom of the tube when positioned at maximum angle. For fixed-angle rotors, this is usually to the bottom of the tube holder. For swinging-bucket rotors, measure when buckets are horizontal.

Common Protocols

  • 300 × g: Cell pelleting (5-10 min)
  • 2,000 × g: Bacteria pelleting (10 min)
  • 10,000 × g: Protein precipitation (10 min)
  • 12,000 × g: DNA/RNA precipitation (15 min)
  • 100,000 × g: Ultracentrifugation

Why RCF Instead of RPM?

RCF is standardized and reproducible across different centrifuges. The same RPM produces different RCF values on rotors with different radii. Always use RCF in protocols to ensure consistent results regardless of the centrifuge model.

Safety Tips

  • Balance tubes carefully (within 0.1g)
  • Never exceed rotor's maximum speed
  • Check tubes are rated for intended RCF
  • Use appropriate adapters for small tubes
  • Ensure lid is properly closed

FAQ

Q: Why do protocols specify RCF not RPM?
A: RCF is independent of rotor size, ensuring reproducible results across different centrifuges.

Q: How do I find my rotor radius?
A: Check the rotor manual or measure from center to the bottom of a tube at maximum angle.