Centrifuge Speed Calculator

What Is Relative Centrifugal Force?

Laboratory centrifuges spin samples at a set RPM (revolutions per minute). The effective gravity on the sample depends on rotor radius and speed. Relative centrifugal force (RCF), also called g-force, compares that acceleration to Earth's gravity.

RPM and RCF Formulas

Convert RPM to RCF using rotor radius in millimeters:

$$\text{RCF} = 1.118 \times 10^{-5} \times r_{\text{mm}} \times \text{RPM}^2$$

Solve for RPM when you know the target RCF:

$$\text{RPM} = \sqrt{\frac{\text{RCF}}{1.118 \times 10^{-5} \times r_{\text{mm}}}}$$

Example: a 100 mm rotor at 10,000 RPM produces about 111,800 × g. Always measure radius from the rotation axis to the bottom of the tube, not the rotor edge.

Related tools: Schmidt Number Calculator and Pump Calculator.

Frequently Asked Questions

What is the difference between RPM and RCF?

RPM counts rotor revolutions per minute. RCF (× g) is the actual centrifugal acceleration relative to gravity and depends on both RPM and rotor radius.

Why does rotor radius matter?

Samples farther from the axis travel faster in a circle, so the same RPM gives higher g-force on outer tubes. Protocols written in × g stay consistent across rotors.

Where do I measure rotor radius?

Measure from the center of rotation to the point where your sample sits—usually the bottom of the tube during the run.

What RCF is typical for cell pelleting?

Many mammalian cell pellets use 300–800 × g for a few minutes. Bacterial pellets often need 3,000–10,000 × g depending on strain and volume.

Can I use centimeters instead of millimeters?

This calculator expects millimeters. Multiply centimeters by 10 before entering radius, or use the formula with r in cm and factor 1.118 × 10⁻² instead.

Report

What Is Relative Centrifugal Force?

RPM and RCF Formulas

Frequently Asked Questions

Related Tools

Recent Visits

Finance Calc Kit