1,006.2
× g
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1,006.2
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1,006
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The RPM to RCF Converter translates centrifuge speed in revolutions per minute into Relative Centrifugal Force (g-force). Protocols often specify centrifugation in units of × g (RCF) rather than RPM because the actual force experienced by a sample depends on both speed and rotor radius.
Since different centrifuges have different rotor sizes, using RCF ensures reproducibility across laboratories. Enter your RPM and rotor radius to find the equivalent g-force.
Relative Centrifugal Force is calculated using the standard formula:
RCF = 1.118 × 10⁻⁵ × r × RPM²
Where r is the rotor radius in centimeters (measured from the center of rotation to the bottom of the tube) and RPM is the rotational speed. The constant 1.118 × 10⁻⁵ combines the unit conversions and the factor (2π/60)²/g.
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Running a centrifuge at 1,200 RPM with a 15 cm rotor radius produces approximately 242 × g, suitable for pelleting most mammalian cells.
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A microcentrifuge at 13,000 RPM with an 8 cm radius generates about 15,108 × g, commonly used for DNA/protein precipitation.
RPM (revolutions per minute) is simply the rotational speed of the centrifuge. RCF (relative centrifugal force), measured in units of × g, is the actual force exerted on the sample. Two centrifuges spinning at the same RPM will produce different g-forces if their rotors have different radii.
Check your centrifuge manual or rotor specifications. The radius is measured from the center of the rotor spindle to the bottom of the sample tube when in the rotor. For fixed-angle rotors, measure to the bottom of the tube slot. Most manufacturers list this in their documentation.
Specifying RCF ensures that the same force is applied to samples regardless of which centrifuge is used. This is important for reproducibility because different centrifuges with different rotor sizes produce different forces at the same RPM. Using RCF eliminates this variability.
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