Convert between RCF (g-force) and RPM for any centrifuge rotor. Enter your rotor radius (in cm) and either the RPM or RCF value — the calculator returns the missing parameter using the standard formula RCF = 11.18 × r × (RPM/1000)². Useful for matching centrifugation conditions across different machines in the lab.
Result
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RCF (× g)
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Speed (RPM)
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Rotor Radius Used
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Use the formula: RCF = 11.18 × r × (RPM / 1000)², where r is the rotor radius in centimeters. For example, at 5,000 RPM with an 8.5 cm radius, RCF = 11.18 × 8.5 × (5)² = 2,385 × g.
Rearrange the RCF formula: RPM = √(RCF / (11.18 × r)) × 1000, where r is the rotor radius in centimeters. Enter your target RCF and rotor radius into the calculator above to get the required RPM.
Using a typical rotor radius of 8.5 cm: RCF = 11.18 × 8.5 × (14)² = 11.18 × 8.5 × 196 ≈ 18,615 × g. The exact value depends on your specific rotor radius — always check the rotor specifications.
RPM (revolutions per minute) describes how fast the rotor spins, but the actual force on your sample also depends on rotor size. RCF (relative centrifugal force, expressed as × g) is the universal measure of the force applied, independent of the centrifuge model. Two centrifuges set to the same RCF will produce identical separation results even if their RPMs differ.
Yes — RCF and g-force are the same thing. RCF is expressed as multiples of Earth's gravitational acceleration (9.81 m/s²), so a value of 2,000 × g means the centrifugal force is 2,000 times gravity. The unit '× g' and RCF are interchangeable in centrifugation contexts.
RCF is machine-independent. If a protocol specifies 3,000 × g, you can run it on any centrifuge by calculating the correct RPM for your specific rotor. RPM settings from one centrifuge may produce very different forces on another centrifuge with a different rotor size.
The rotor radius (also called the maximum radial distance, r-max) is listed in your centrifuge manual or on the manufacturer's rotor data sheet. It is measured in centimeters from the center of the rotor axis to the tip of the sample tube. Common values range from about 5 cm to 20 cm.
Cell pellets typically require 200–800 × g; bacterial cells 3,000–5,000 × g; subcellular organelles 10,000–20,000 × g; and ultracentrifugation for ribosomes or viruses can exceed 100,000 × g. Always follow your specific protocol for the best results.