RCF/RPM Calculator

Convert between RPM and relative centrifugal force (× g) for any rotor radius. Batch mode, methods-section snippet, and CSV export. Data never leaves your browser.

RPM ↔ RCF ↔ RadiusBatch ModeMethods Snippet

Try it out

Load example centrifuge protocol data to see the full workflow

rpm

RCF

18,625.9 × g

RPM

14,000

RCF

18,625.9 × g

Radius

85.0 mm

Rotor cross-section
Centerr = 85.0 mm

Radius is measured from the center of rotation to the bottom of the tube (rmax). This is the distance used in all RCF calculations.

  • Converting between RPM and RCF for a centrifuge protocol
  • Planning centrifugation settings for a different rotor than the protocol specifies
  • Writing a methods section that requires RCF reporting
  • Batch-converting multiple protocol steps at once

Don't use for

  • Continuous-flow centrifuge calculations (different physics)
  • Industrial-scale decanter centrifuge sizing
  • Density gradient optimization (see Separation Estimator tool, coming soon)

What is RCF?

RCF (relative centrifugal force) measures the actual force applied to a sample, expressed as multiples of gravitational acceleration (×\times g). Unlike RPM, RCF accounts for rotor radius — the same RPM on two different rotors produces different forces.

RCF is the reproducible unit. If a protocol says 'centrifuge at 300 ×\times g,' any rotor at the correct RPM for its radius will produce the same separation.

How to Measure Rotor Radius

Rotor radius is the distance from the center of rotation to the bottom of the sample tube (or the furthest point of the sample in the tube). This is NOT the rotor diameter. Check your rotor manufacturer's documentation for the exact r_max value.

Common mistake: using the rotor arm length instead of the full distance to the tube bottom. Always measure to the furthest point the sample reaches.

RCF in Methods Sections

Most journals require centrifugation forces reported as ×\times g (RCF), not RPM. Reporting RPM alone is insufficient because readers with different rotors cannot reproduce the conditions. Always include both RPM and RCF, plus rotor model if possible.

Use this calculator's 'Copy for Methods' button to generate a properly formatted statement you can paste directly into your manuscript.

Frequently Asked Questions