It is much better to use g (the capital G is not the correct unit) as a unit for centrifugation steps, which refers to the acceleration applied to your samples (so 10,000 g means 10,000 times Earth's gravitational force).

RPM (revolutions per minute) is not as useful a unit, because the force varies with the radius of your machine (the bigger the radius, the more acceleration is applied to your samples for the same RPM).

Using g, you can easily replicate experiments.

g = (1.118 × 10-5) R S2 where g is the relative centrifugal force, R is the radius of the rotor in centimeters, and S is the speed of the centrifuge in revolutions per minute.

For some centrifuges, there is a button "rpm/ rcf" for automatic conversion of the rpm-value in g

Hi Aamir,

G is the G force whilst RPM is refs per minute. The below links might be of use. The first one is a converter calculator with a list of different centrifuge models so as to know the radius whilst the second link is an explanation of the differences between them.

http://www.endmemo.com/bio/grpm.php

http://clinfield.com/2012/07/how-to-convert-centrifuge-rpm-to-rcf-or-g-force/

http://wiki.answers.com/Q/Difference_between_g_and_RPM_in_centrifugation?#slide1

G is the gravitational force and rpm is revolution per minute. These are dependent on the radius of the centrifuge.

http://www.endmemo.com/bio/grpm.php

formula is

RPM = 1000*sqrt of (750/1.2r) where r is the radius of the rotar in mm.

On a more practical perspective, if you describe a centrifugation step in your protocol in Gs, then it can be easily replicated in any other lab with any other equipment.

It is much better to use g (the capital G is not the correct unit) as a unit for centrifugation steps, which refers to the acceleration applied to your samples (so 10,000 g means 10,000 times Earth's gravitational force).

RPM (revolutions per minute) is not as useful a unit, because the force varies with the radius of your machine (the bigger the radius, the more acceleration is applied to your samples for the same RPM).

Using g, you can easily replicate experiments.

Different units for calculating the centrifugal operation.

Most of the general labs use 'rpm' conventions.

The ultracentrifuges and even tabletop higher versions use both the conventions.

Use according to the given formula below (jpg).

But 'g' is not to be confused with acceleration due to gravity.

Rather in this context, it is somewhat centrifugal force convention.

'g' is the symbol written for 'rcf' values. relative centrifugal force.

For example, 10 X g. In this context, It is neither gram nor gravity. It is relative centrifugal force of the centrifuge tubes to the machine at 10:1 ratio.

It is advisable to always use 'g' values in your publications. If you use a centrifuge machine with the speed measured in rpm, convent it into 'g' using the equation stated by Xiang Wang or Subash Malik above. And also, where the speed is in 'g' and you have to replicate it in you lab using your centrifuge machine, remember to work it out or select what is applicable on your machine. Where you have to measure the radius, do it from the centre of the rotor to the tip of the bucket in the rotor.

RPM reffers to how many Revolutions yor centrifuge gets in a minute and G is how many times the gavity force is applied to your samples.

Two centrifuges with the same RPM may not aplly the same G force on your samples since the inclination and radius may differ between centrifuges.

Is better to use G force than RPM since, G is Standard and you can calculate it in order to develop an experiment, but RPM will not always represent the same force in diferents machines.

You can Use this calculator to determine the G force/ RPM in differents centrifuges with the inclued list of machines below.

http://www.endmemo.com/bio/grpm.php

Just because transfer of experiments from one rotor to another came up in the discussion, this requires knowledge not only of the relative centrifugal force (relative means normalized to the earths gravitational force g = 9.81 m/s^2), it also requires the geometry of the rotor expressed as pelleting efficiency: k = t/S = ln(r_max/r_min) * 253303 / (rpm/1000)^2, with t = time required for sedimentation, S the sedimentation coefficient of the particle, r_max and r_min the maximal and minimal radius of the rotor. Then for two different rotors k_1/t_1 = k_2/t_2.

You can also use this relationship to estimate the time if you can no longer use the maximum speed, e.g., because your rotor has been derated. Then the new pelleting efficiency k' = k * (rpm_max / rpm_now)^2.

You may want to read up on the theory of centrifugation for example in chapter 25 of my book on the Biophysical Chemistry of Proteins (2011), The DOI is 10.1007/978-1-4419-7251-4_25

Hi,

Modern day ultra-centrifuges can generate forces in excess of 300,000 times that of gravity, forces sufficient to overcome the very cohesion of most molecules (including the metal of the rotor). The force is usually given as some value times that of gravity.

The centrifugal force is dependent upon the radius of the rotation of the rotor, the speed at which it rotates, and the design of the rotor itself (fixed angle, vs swinging bucket). Rotor speed and design can be held constant, but the radius will vary from the top of a centrifuge tube to the bottom. If a measurement for the radius is taken as the mid-point, or as an average radius, and all forces are mathematically related to gravity, then one obtains a relative centrifugal force, labeled as x g. Centrifugation procedures are given as x g measures, since RPM and other parameters will vary with the particular instrument and rotor used. Relative Centrifugal Force is a constant that is independent of the apparatus used.

Calculation of R.C.F. for a given radius and RPM. A simple formula for calculating this value is:

RCF = 1.12r (RPM/1000)^2

where r = radius in millimeters

RPM = revolutions per minute

The difficulty with using the formula is establishing the value for r. Typically, there are three r values given (by the manufacturer) for a rotor: the maximum, minimum and average r. These correspond to the distances from the center of rotation to the bottom, top and middle of the sample tube.

Debabrata

IISER-Kolkata

New generation of centrifuges, there is a button "rpm/ rcf" for automatic conversion of the rpm-value in g.

Debabrata brings up a good point regarding the difference in radius from the top of the centrifuge tube to the bottom. The actual RCF experienced at different depths within the tubes can therefore vary. This effect will be more pronounced when using a centrifuge with a small diameter rotor.

Tom

The force exerted on a particle in a centrifuge is a simple function of the rotation speed of the centrifuge and the radius of rotation. The actual equation is:

RCF or G-force= 1.12 x R x (RPM/1000)²

where R is the radius of rotation measured in millimetres.

G depends on the diameter of the rotor.

try with these page:

http://www.geneinfinity.org/sp/sp_rotor.html

:D

Hello, it's OK if the author indicated the centrifugal force depending on g. Nowadays all centrifuges (I hope) display rotation speed both in RPM and g. But on the centrifuge's control panel g is actually RCF. So, if you programme the centrifuge at 10000 RCF there will be 10000 x g.

Like other colleagues had said it's better use "g", not RPM because g is stable, always is the same. Modern centrifuges have a botton for conversión between g (RCF) and RPM.

Any time one refers to centrifugation of a sample in a journal paper it should be in g force and not in rpm . The g force is the absolute centrifugal force applied on the sample for sedimentation which does not change with the rotor conditions or centrifuge. Whereas the rpm differs based on the rotor and the centrifuge tube used and is dependent on the radus of the rotor. There is a formula to convert g(RCF) to RPM which is available in books dealing with centrifugation. RPM is OK when one specifies the centrifuge and the rotor or when is only for precipitation in a clinical or ordinary centrifuge.

Check this site for conversion

http://www.endmemo.com/bio/grpm.php

The best and easiest way would be that you find the calculator on the site

http://www.endmemo.com/bio/grpm.php,  fill in the given boxes  values obtained in rpm and the measurement of radius of rotor of your centrifuge, and just click, you will get the calculated equivalent value of RCF expressed in g.

RPM (rotations per  minute) and RCF (relative centrifugal force or x g-force, the number of times the gravitational force) are two different parameters. RPM stands for the number of rotations per minute that the rotor (of any size) of a centrifuge does during centrifugation. The x g is for the force (number of times the gravitational force) exerted on the centrifuge tube and its contents during centrifugation and is the basis of separation of components in the mixture being centrifuged. Also g value varies with the size of the rotor and RPM; the greater the radius of the rotor that is usually taken as the average through the height of the centrifuge tube (r average) (however, if the protocol targeted separation by pelleting the desired component then the radius should be measured throughout the entire centrifuge (r maximum). The function between these two parameters follows the equation: RCF = 1.2 r (RPM/1000)(RPM/1000) where r is in millimeters. In writing reports especially for journal publications, authors are advised to indicate x g and not just RPM in the materials and methods section. Two centrifuges used at the same RPM setting may have different capacities to separate the components of a given mixture by centrifugation. For the purpose or checking on the repeatability of the study, RCF is required to be reported than simply RPM.

Evangelina has given a lucid explanation of both the units.

Can anybody give some reference for citation for the equations that are discussed here? Is those websites can be cited for a journal article? Or I need to cite a published journal article or book? If any body has the name of the book please provide that also. Thank you.

can u say anyone, formula for how to convert g to rpm in centrifugation

I suggest you better read any of the following papers:

1. Michael Pendleton (2006) Descriptions of melissopalynological methods involving centrifugation should include data for calculating Relative Centrifugal Force (RCF) or should express data in units of RCF or gravities (g), Grana, 45:1, 71-72, DOI: 10.1080/00173130500520479

2. Lieux, M. H. (1980). Acetolysis applied to microscopical honey analysis. Grana, 19, 57–61.

3. Louveaux, J., Maurizio, A. & Vorwohl, G. (1970). Methods of melissopalynology. Bee World, 51, 125–138.

the attachment file explain the RPM and g (RCF) meaning

i think that the beast way iis the equation below

g=(1.118x10-5)R S2

where Ris the radiuos

S is the RPm

As I had stated in my earlier response, x g and rpm are two different values; x g stands for the force (number of times the gravitational force, g) exerted on the centrifuge tube (also referred to as the relative centrifugal force, RCF) and its contents during centrifugation and is the basis of separation of components in the mixture being centrifuged. RPM stands for the rotor setting indicating the number of revolutions per minute and this does not serve as the basis of separation by centrifugation. One RPM setting may give two RCF values, depending on the radius of rotation given a kind of rotor installed in the said centrifuge; likewise, two rpm values may give one RCF value, again depending on the rotor's radius. The function between RCF and RPM follows the equation: RCF = 1.2 r (RPM/1000)(RPM/1000) where r is the radius of the rotor in millimeters.

The above discussion sufficiently explains the point in question. So, no need to repeat the same thing in different words.

The G is the total force of centrifugation

RPM is the rotator speed , which was one part of the G force

G force were combine of RPM + center of the centrifugator to tube distance

We can calculate or find the absolute G force Via Normogram.

 how can we convert rpm to g because i have the centrifuge which can not automaticaly convert the rpm to g there is only one button for rpm so how can I convert rpm to g can any body help me please...

Sadia, look on page 1 in this discussion, there are great "popular answers" on the top :-)

Here is simple calculator, which Compute Relative Centrifugal Force (RCF) or G-force

or

Compute revolutions per minute (rpm)

http://insilico.ehu.es/mini_tools/rcf_rpm.php

hello,

I do get the information above, but still i have some difficulty using the machine. i am expected to use 1800g for the centrifugation according to an article. does this mean i need to set the machine RCF setting to 1800 or 1800*9.8? does this depend on the model of the machine or not?

Hi,

Im working on phytic acid and Pi analysis but Im using 1000 RCF in the centrifuge machine for 1000 g. I think RCF and g is same.  most of centrifuge have given with RPM/RCF option which you can select it.

 further more, you can use following calculator for G force/RPM conversion.  

http://www.geneinfinity.org/sp/sp_rotor.html

Kishor thanks. I agree with you. But I had to make sure. Fortunately our machine has the RPM/RCF option too. 

I want to calculate rpm but the machine I have in my lab that calculates RCF. How to convert RCF into RPM?

To calculate the rpms you need in order to acquire a specific RFC or "G-Force" you would have to convert the formula RCF = 1.119 x 10-5 (rpm)2 (x) to solve for RPM; where x is the radius of rotation in centimeters.

 I come up with RPM = the square root of [G/(x) (1.119 x 10-5)].

The relationship between G and rpm and the formula for their conversion are available on the net and have been discussed earlier well in detail on Research Gate also.

value of G is grater than rpm value, by a simple formula

   rpm = 1100 + G

RPM (revolutions per minute) is only the speed of rotation, does not take into account the size of the radius of the rotor, eg To obtain the real centrifugal force (RCF) ~ Force G, it is necessary to calculate G = 1.12 x R x (RPM / 1000) ²

The relationship between RPM and RCF is as follows:

g = (1.118 × 10-5) R S2

Where g is the relative centrifugal force,

R is the radius of the rotor in centimeters ( from center of rotor to sample),

and S is the speed of the centrifuge in revolutions per minute (rpm).

you can use following calculator

http://nidacon.com/rpm/

RPM stands for "Revolutions per minute." This is how centrifuge manufacturers generally describe how fast the centrifuge is going. The rotor, regardless of its size, is revolving at that rate. The force applied to the contents varies by the size of the centrifuge rotor.

RCF (relative centrifugal force) is measured in force x gravity or g-force. This is the force exerted on the contents of the rotor, resulting from the revolutions of the rotor.

It is RCF, not RPM that separates aqueous solutions in the centrifuge. RPM can be calculated for any centrifuge by this equation:

RCF = 1.1118 x 10-5 x r x rpm2

Where r is the rotor radius in centimeters

Enough has been said on the relationship of RPM and RCF or x g in this discussion. So useless to keep harping on the same string repeatedly; just have a look on the several explanations given here, and everything will be clear regarding the conversion of one unit to the other.

http://www.endmemo.com/bio/grpm.php

Where you can find g equvalent of RPM's of popular Centrifuge machines or you can calculate by entering required radius of the machine and RPM value.

G is the G force whilst RPM is refs per minute.

RPM measures how fast the rotor is spinning. It is impossible to measure the gravitational force being applied. RCF adaps the rotor size into its measurement, so is possible to determine the gravitational force being applied.

Agreed.

do some search, please!

info from http://www.endmemo.com/bio/grpm.php

G force refers to Relative Centrifugal Force (RCF).

RCF is positively related with the rotor radius and the rotation speed of the centrifuge.

The g force rpm conversion formula is as follows:

RCF = 1.118 * 10-5 * r * (rpm)2 Where: RCF: Relative Centrifuge Force, in "g" r : Rotor radius, in "cm" rpm: Rotation speed, rotations per minute, in "rpm"

I agreed with your answer. Now a most of the researcher are using g instead of rpm because its very difficult to replicate the experiment.

Im also using this website

Thanks @Berk and Casilda

It is my pleasure follow this question

RPM this is fast of the centrifuge, while RCF is measured in force x gravity or g-force.

RPM and g are inter-convertable. But sci unit is g. Most of journals ask to write g for centrifuge units instead of RPM.

Certain procedures necessitate precise centrifugation conditions, which must be specified in terms of relative centrifugal force (RCF) expressed in units of gravity (times gravity or × g). Many microcentrifuges only have settings for speed (revolutions per minute, RPM), not relative centrifugal force. Consequently, a formula for conversion is required to ensure that the appropriate setting is used in an experiment. The relationship between RPM and RCF is as follows: g = (1.118 × 10-5) R S2 Where g is the relative centrifugal force, R is the radius of the rotor in centimeters, and S is the speed of the centrifuge in revolutions per minute. Values of RCF in units of times gravity (× g) for common microcentrifuge rotor radii appear in the following conversion table. As an example, centrifugation of a sample at 5,000 RPM in a microcentrifuge that has a rotor with a radius of 7 cm will deliver a centrifugal force of 1,957 × g. Centrifugation speed and time often are not critical factors in routine sample-handling procedures involving a benchtop microcentrifuge. Usually, as long as speed and time are sufficient to ensure that cells, debris or resin are pelleted effectively, it does not matter if the speed is faster or the time longer than necessary. For this reason, many protocols do not specify a particular centrifugal force to be applied but instead indicate some general guideline such as “centrifuge at high speed for 1 minute.”

g = 1.12 × r (RPM/1000)2 where

g= the relative centrifugal force (RCF)

r = the radius of the rotor in centimeters

RPM = speed of the centrifuge in revolutions per minute

Following

Following

A firm measures require precise centrifugation conditions, which must be precise in terms of relative centrifugal force (RCF) articulated in units of gravity (times gravity or × g). Many microcentrifuges only have settings for speed (revolutions per minute, RPM), not relative centrifugal force. Consequently, a formula for alteration is required to ensure that the appropriate setting is used in an experiment. The relationship between RPM and RCF is as follows: g = (1.118 × 10-5) R S2 Where g is the relative centrifugal force, R is the radius of the rotor in centimeters, and S is the speed of the centrifuge in revolutions per minute. Values of RCF in units of times gravity (× g) for common microcentrifuge rotor radii. As an example, centrifugation of a sample at 5,000 RPM in a microcentrifuge that has a rotor with a radius of 7 cm will deliver a centrifugal force of 1,957 × g. (Thermo Scientific)

Relative Centrifugal Field (RCF)

Relative centrifugal field (RCF) describes and compares the strength of the fields generated by different size rotors and different operating speeds. Just as length is measured in units of inches or millimeters, time in units of hours or minutes, the relative centrifugal field is measured in units also. It is expressed in multiples of the earth’s gravitational field, abbreviated g.

How to calculate the centrifugal field strength

There’s a simple formula for calculating the strength of a particular centrifugal field:

where r stands for the radius, which is the distance in millimeters (mm) from the center of rotation to some point within the rotor, and RPM is the speed of rotation in revolutions per minute (rpm). Sometimes radial distances are given in centimeters. Before using them in this equation, you must first convert them to millimeters (multiply by 10).

How to determine maximum RCF of a centrifuge rotor

To find the maximum RCF of a rotor, you need to know its maximum speed and its maximum radius (rmax), and the distance from the center of rotation to the bottom of the rotor cavity or bucket during centrifugation (see illustration below). Almost all centrifuge manufacturers publish this information for their rotors in their instruction manuals.

📷

For example, the maximum RCF of the JS-4.2 rotor can be obtained from its maximum speed (4200 rpm) and its rmax (254 mm) as follows:

📷

If this same rotor is run at a lower speed, say 2000 rpm, the RCF it generates will also be lower:

📷

Since the RCF varies with the square of the rotor speed, you can see that any change in speed will cause a much greater change in RCF.

http://tools.thermofisher.com/content/sfs/brochures/TR0040-Centrifuge-speed.pdf

This link explains RPM vs G clearly.

Thanhs for all, it is good informatios.

I agree with Daniel Lorenz Winter

Use small g, not G for pointing to unit, g unit is the correct and scientific.

g: is the g force.while

RPM: (revolutions per minute)

g = 1.12 × r (RPM/1000)2

 where:

g= the relative centrifugal force (RCF)

r = the radius of the rotor in centimeters

RPM = speed of the centrifuge in revolutions per minute

The relationship between revolutions per minute (RPM) and relative centrifugal force (xg) is:

g = (1.118 × 10-5) R S2

where g is the relative centrifugal force, R is the radius of the rotor in centimeters, and S is the speed of the centrifuge in revolutions per minute.

So, you can use this for any centrifuge, just measure the radius of the rotor from the center to outer edge, then use formula.

http://www.endmemo.com/bio/grpm.php

this link might help is a calculator for RPM RCF and radius according to rotor theres references values

The link pointed out by Katerina Kouzari solves the whole problem and presents information on the various rotors in use.

The whole matter can be resolved by simple basics from any chapter "MECHANICS" from a school PHYSICS book:

http://www.youscreen.de/axvnyceye31.jpg

Keep in mind that:

Firstly: g is lower at the äquator (g=9.78) and highest at the poles (g=9.84) as earth is rotating too

Secondly: effective centrifugal acceleration differs WITHIN the vials rotating!! Filled to the very top the effective radius is remarkably reduced, so is the x times g acceleration too: half the radius reduces centrifuge acceleration that may result in tinier pellets, reduced efficiency!! Use many vials with less filling in opposite centrifuges positions. Always BALANCE ROTOR in opposite places, avoid severe accidents!!! 12.000 xg will result in severe damage to lab and people in range! 1ml+1g vial behaves like a 24 kg mass approachig you at the respective tangential velocity (cannon ball!) Consider of broken rotors spindle too....

Thirdly: g is no force but an acceleration! When multiplied by mass giving you a force in Newton.

If still in doubt ask any 15 to 16 year old pupil, they had in Physics, a nice portion of delicious ice-cream might help to make them remember and willing to explain the respective formulas.

In case of no sweets available, watch this lecture(s):

https://www.youtube.com/watch?v=WQ9AH2S8B6Y

Perfect answer

RPM (revolutions per minute) is not as useful a unit,

Always used correct "G" calculated through formula. RPM may be changed due to different size of centrifuges rotters..

Great Information Daniel.....

You can find the related formulas as well as an online calculator here:

http://molbiotools.com/centrifugationcalculator.html

Fully explained and illustrated answer. Others also have amply clarified in their answers. This is mentioned in almost all text books of laboratory medicine. Shall we put an end to this discussion ?

You can also use this table if you are not familiar with the calculations.

best

Francisco

Yes! I agree with Patel. This discussion is over-flogged. It needs to end