RCF / RPM Centrifuge Calculator
RCF = 1.118 × 10⁻⁵ × r(cm) × RPM²
Convert between centrifuge speed in rpm and relative centrifugal force in × g using the rotor radius you enter.
Inputs
Distance from the rotation axis to the sample.
Result
13684 × g
12000 rpm at a radius of 8.5 cm corresponds to 13684 × g.
Calculation
Relative centrifugal force
RCF = 1.118 × 10⁻⁵ × r(cm) × RPM²
Substitution
RCF = 1.118 × 10⁻⁵ × 8.5 × 12000²
RCF = 13684 × g
Inputs
- Rotor radius
- 8.5 cm
- Speed
- 12000 rpm
- RCF
- 13684 × g
The applicable radius depends on the rotor geometry and on where the sample sits. Manufacturers report minimum, maximum and average radii — use the one your protocol or rotor manual specifies.
No rotor radius is assumed for you: the value above is the one you entered.
RCF is a multiple of standard gravity and is dimensionless; “× g” is a label, not a unit conversion.
What the radius means
- Radius
- 8.5 cm
- Speed
- 12000 rpm
- Force
- 13684 × g
The radius is measured from the rotation axis to the sample. Rotor manuals quote minimum, maximum and average radii — the RCF at the tube bottom is higher than at the meniscus, so use the radius your protocol specifies.
About this calculator
Protocols specify centrifugation either as a rotational speed (rpm) or as a relative centrifugal force (RCF, written “× g”). The two are only interchangeable once the rotor radius is known, because the force experienced by the sample grows with both the square of the speed and the distance from the rotation axis.
The constant 1.118 × 10⁻⁵ applies when the radius is given in centimetres and the speed in revolutions per minute. Radii entered in mm or m are converted to cm first, and the converted value is shown in the calculation steps.
No rotor radius is assumed. Manufacturers publish minimum, maximum and average radii for each rotor and adapter combination; RCF at the bottom of a tube is higher than at the meniscus. Use the radius that your rotor manual or protocol specifies.
LabReadyTools is provided as a calculation aid. Users remain responsible for verifying calculations, units, chemical compatibility, experimental procedures and applicable safety requirements before laboratory use.
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