Unfortunately g's are a function of rpms and the radius from the axis of rotation, so there isn't a direct conversion that will work for every centrifuge since the radius will vary depending on the model of centrifuge. However, you may be able to find your centrifuge's rotor here and just use their calculator.
G force depends on rpm and the radius. You can use the following equation for the conversion : g Force (RCF) = (rpm)2 × 1.118 × 10-5 × r (where r is the rotational radius in centimeter)
Rmax will give you the g force at the bottom of the tube, Rmin will give you the g force at the top of the tube - usually the g force quoted in a protocol is the R max value, but it may be the Raverage.
VERY VALUABLE INFORMATION PUT BY AUTHORS.....I THINK THIS WAS THE REASON THAT WHAT I READ FOR PRF PREPARATION THAT 3000 RPM FOR 10 MINUTES IS ENOUGH.....BUT I REQUIRE 30 MINUTES, BECAUSE PROBABLY I USE CENTRIFUGE MACHINE WITH DIFFERENT RADIUS
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.
You can use this for any centrifuge, just measure the radius of the rotor from the center to outer edge .
see this online tool : http://www.labtools.us/centrifugation-speed-rpm-to-g-conversion/
where S is the speed of the centrifuge (RPM), g is the relative centrifugal force, R is the radius of the rotor {distance from the centre of rotor to the sample (in cm)}.
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. Radius should be calculated as the distance from the center of the rotor to your sample (not to outer edge)
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. You can use this for any centrifuge, just measure the radius of the rotor from the center to outer edge
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):
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. Radius should be calculated as the distance from the center of the rotor to your sample (not to outer edge)
Relative Centrifugal Force (RCF) or g force is the acceleration applied to the sample. RCF is relative to the force of Earth’s gravity and depends on revolutions per minute (RPM) and radius of the rotor.
A simple formula for calculating this value is:
RCF = 1.12 × R × (RPM/1000)2
R = Radius of rotation measured in millimeters
RPM = revolutions per minute
Note: RCF is more precise than RPM because the rotor size might differ, and RCF will be different while the revolutions per minute stay the same.
"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."