LABORATORY INSTRUMENT UTILITIES

RCF to RPM Calculator

Calculate relative centrifugal force (RCF), RPM, and rotor radius conversions for centrifugation workflows and laboratory instrument setup. Convert between × g and revolutions per minute, compare centrifuge settings across different rotors, and standardize protocols between instruments and laboratories.

Conversion Inputs

Enter the rotor radius and choose the conversion direction for your centrifuge setup.

Conversion mode *

Rotor radius *

Measure rotor radius from the center of rotation to the center of the sample position. Do not measure to the rotor chamber wall, rotor outer edge, or centrifuge housing.

RCF / × g *

RPM *

Rounding preference

Results

RCF and RPM are not interchangeable. The same RPM can produce different × g values depending on rotor radius.

Export Summary

Formula and Calculation Logic

RCF and RPM are related, but they are not the same measurement. RPM describes how fast the rotor spins, while RCF describes the force applied to the sample. Because RCF depends on rotor radius and RPM, the same RPM can produce different centrifugation forces in different rotors.

Use rotor radius in centimeters for all calculations.

RCF = 1.118 × 10^-5 × radius × RPM²

RPM = √(RCF / (1.118 × 10^-5 × radius))

Where RCF is relative centrifugal force in × g, RPM is revolutions per minute, and radius is measured in centimeters at the effective sample position. Tube adapters and rotor geometry can change the effective radius.

Example Workflow

A protocol says to centrifuge samples at 10,000 × g for 5 minutes, but the centrifuge requires RPM.

Select RCF to RPM as the conversion mode.

Enter 10,000 as the RCF / × g value.

Enter the rotor radius in centimeters, or convert from mm or inches.

Use the calculated RPM or suggested rounded setting on the centrifuge.

Common Mistakes

Using RPM from another centrifugeRotor radius may differ, which changes the actual RCF.

Entering rotor diameterThe formula requires radius, not diameter.

Ignoring adaptersAdapters can change the effective sample radius.

Equating RPM with × g10,000 RPM does not necessarily mean 10,000 × g.

FAQ

Is RCF the same as × g?

Yes. RCF is commonly reported as × g. A spin at 10,000 × g means the sample experiences 10,000 times the force of gravity.

Why do protocols use RCF instead of RPM?

RCF is more transferable between centrifuges because it accounts for rotor radius. RPM alone only describes rotor speed.

Can I use the same RPM on a different centrifuge?

Not reliably. A different rotor radius can produce a different RCF at the same RPM.

Where do I find rotor radius?

Check the centrifuge rotor manual, manufacturer documentation, or rotor label. Use the radius to the actual sample position, especially when adapters or angled rotors are used.

Should I round the RPM result?

Usually yes. Most centrifuges are set in practical increments, such as 10 or 100 RPM. Use exact values only when the protocol requires strict settings.

These calculators are intended for research and educational workflows only. Always validate calculations, units, and experimental conditions before laboratory use.