11,180
× g
1,047.2
rad/s
104.72
m/s
109,662.3
m/s²
0.1
m
11,180
× g
1,047.2
rad/s
104.72
m/s
109,662.3
m/s²
0.1
m
The Centrifuge Calculator converts rotational speed (RPM) and rotor radius into Relative Centrifugal Force (RCF), commonly expressed as multiples of Earth's gravitational acceleration (× g). Laboratory centrifuges are indispensable in biology, chemistry, and medicine for separating substances by density — from blood components and cell pellets to DNA and nanoparticles.
Centrifuge protocols specify RCF in × g rather than RPM because the separation force depends on both speed and rotor radius. Two different centrifuges at the same RPM will produce different g-forces if their rotors have different radii. The standard conversion formula is: $$\text{RCF} = 1.118 \times 10^{-5} \times r \times \text{RPM}^2$$ where r is the rotor radius in centimeters.
This calculator also provides the angular velocity in rad/s, the tip speed of the rotor, and the raw centripetal acceleration in m/s². These values are critical for rotor safety analysis — exceeding the maximum rated speed can cause catastrophic rotor failure. Ultracentrifuges operating at 100,000+ RPM generate forces exceeding 500,000 × g and require vacuum chambers and armored containment.
The calculator uses the standard RCF formula used in every laboratory centrifuge manual:
$$\text{RCF} = 1.118 \times 10^{-5} \times r_{\text{cm}} \times \text{RPM}^2$$
This is derived from the centripetal acceleration formula: $$a_c = \omega^2 r = \left(\frac{2\pi \cdot \text{RPM}}{60}\right)^2 \times r$$
Dividing by g = 9.81 m/s² and converting radius to centimeters gives the 1.118 × 10⁻⁵ constant.
Angular velocity: $$\omega = \frac{2\pi \times \text{RPM}}{60}$$ in rad/s.
Tip speed: $$v = \omega \times r$$ — the linear speed at the outermost point of the rotor, critical for mechanical stress analysis.
Common RCF ranges: 300–500 × g for pelleting cells, 10,000–20,000 × g for mitochondria and bacteria, 100,000+ × g for ribosomes and viruses (ultracentrifugation). If your protocol specifies an RCF and your centrifuge displays only RPM, use this calculator to find the correct RPM for your specific rotor. The tip speed should stay below the rotor manufacturer's maximum rating to avoid structural failure.
Inputs
Results
At 10,000 RPM with a 10 cm radius rotor, the sample experiences 11,180 × g — sufficient for pelleting bacteria and large organelles.
Inputs
Results
At 60,000 RPM with an 8 cm rotor, RCF reaches 321,408 × g with a tip speed of 503 m/s (Mach 1.5!) — requiring vacuum operation.
RPM is simply how fast the rotor spins. RCF (× g) is the actual force experienced by the sample, which depends on both RPM and rotor radius. Two centrifuges at the same RPM produce different g-forces if their rotors differ in size.
RCF ensures reproducibility across different centrifuges. Since F = mω²r, the separation force depends on the radius. Specifying RCF allows any lab to achieve the same force regardless of their specific rotor geometry.
Rearrange the formula: RPM = √(RCF / (1.118 × 10⁻⁵ × r_cm)). For example, to achieve 10,000 × g with a 12 cm rotor: RPM = √(10000 / (1.118e-5 × 12)) ≈ 8,629 RPM.
The rotor may deform or shatter due to the enormous centrifugal stresses. Modern centrifuges have electronic speed limiters and imbalance detectors, but exceeding ratings can cause catastrophic, dangerous failure.
An ultracentrifuge operates above 30,000 RPM (typically 40,000–150,000 RPM), generating forces of 100,000 to over 1,000,000 × g. They operate under vacuum to reduce friction heating and are used for separating proteins, viruses, and subcellular organelles.
Yes. The effective radius (and thus RCF) varies from the top to the bottom of the tube. Most protocols reference the maximum radius (bottom of tube) to ensure the minimum required force is achieved everywhere in the sample.
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