Skip to content
CALX
Appearance

Appearance

Light or dark

Colour
Accessibility

CategoriesSearch

RPM ↔ RCF conversion (relative centrifugal force)

Rotation speed (RPM) to relative centrifugal force (RCF) and back, from the rotor radius.

Parameters

Rotor radius (r)

Actual distance between the rotation axis and the sample, not the diameter.

rpm
× g

Result

ResultRCF

2795.61 × g

Formula
RCF = ω² r / gn = (2π × 5000 / 60)² × 10 cm / 9.80665 = 2795.6 × g
0k5k0629012 60018 90025 200speed (rpm)RCF (× g)5000 · 2800 × g
Curve computed at the entered radius.

Calculation, assumptions and sources

Provisional · Convention · 1 source · reviewed on 25 August 2026

OverviewThe RCF (relative centrifugal force, in × g) from the rotation speed in RPM and the rotor radius, or the reverse, with the exact formula RCF = ω² r / g.

The RCF (relative centrifugal force, in × g) from the rotation speed in RPM and the rotor radius, or the reverse, with the exact formula RCF = ω² r / g. RCF grows as the square of the speed.

Method & formulasRCF = ω² r / g_n
RCF = ω² r / gnω = 2π N / 60

The RCF is the centripetal acceleration ω² r divided by standard gravity g_n = 9.80665 m/s² (a conventional value, 3rd CGPM, 1901). The 1.118 × 10⁻⁵ constant found in protocols (r in centimetres) is the rounded form of 4π² / (3600 × 100 × g_n).

RPM
the rotation speed of the rotor, in revolutions per minute.
r
the rotor radius, the distance between the rotation axis and the sample.
RCF
the relative centrifugal force applied to the sample, in × g.
Validity domainOn a fixed-angle rotor, the radius varies along the tube; protocols specify the radius to use (minimum, maximum or average) and the rotor’s datasheet prevails.

On a fixed-angle rotor, the radius varies along the tube; protocols specify the radius to use (minimum, maximum or average) and the rotor’s datasheet prevails.

ExampleA rotor of 10 cm radius at 5,000 rpm gives ω = 523.6 rad/s and an RCF of 2,796 × g; the rounded constant gives 2,795 × g, a 0.02% difference.

A rotor of 10 cm radius at 5,000 rpm gives ω = 523.6 rad/s and an RCF of 2,796 × g; the rounded constant gives 2,795 × g, a 0.02% difference.

SourcesBIPM

  1. BIPM, 3e CGPM (1901), Déclaration 2 — valeur conventionnelle de g_n, 1901.

    Location: Déclaration 2 : « la valeur adoptée pour l’accélération normale de la pesanteur est 980,665 cm/s² » · accessed 2026-08-25

Scientific validationProvisional, reviewed on 25 August 2026

Provisional · Sources and assumptions are provided; the documentary review is incomplete.

Convention. The result follows the significant figures of the least precise input.

revision 1 · reviewed on 25 August 2026

Revision log

  1. revision 1 · 2026-08-25 · source update

    Rework: the exact formula ω² r / g_n replaces the rounded 1.118 × 10⁻⁵ constant, and g_n is named with its source (CGPM 1901). Effect on results: +0.02%.

    Computed RCF values increase by 0.02% (2,795 → 2,796 × g on the example).