## Find a Centrifuge to Suit Your Needs

### High G-Force STAT Centrifuges

- STAT blood, chemistry, and PPP
- Horizontal centrifugation, 4,000 max xg
- 6, 12, and 24 tube capacity

### Programmable Routine Centrifuges

- Chemistry, coag, and urine
- Horizontal and fixed angle, 2,000 max xg
- 6, 12, and 24 tube capacity

# How to Calculate G-Force:

The Force exerted on a sample in a centrifuge is a function of the rotation speed of the centrifuge (RPM) and the radius of the rotor.

If you know the RPM, the equations to calculate G-Force are:

**In Centimeters: RCF or **G-Force = 0.00001118 x Rotor Radius x (RPM)²

OR

**In Inches: RCF or **G-Force = 0.0000284 x Rotor Radius x (RPM)²

# How to Calculate RPM:

If you know the G-Force you need and you want to calculate the RPM, the equations to calculate the RPM are:

**In Centimeters: **RPM = sqrt(G-Force / (0.00001118 x Rotor Radius))

OR

**In Inches: **RPM = sqrt(G-Force / (0.0000284 x Rotor Radius))

The Rotor Radius is the radius of the rotation measured in centimeters or inches. For example, in the photograph below – The Rotor Radius is 12.7 cm

For example, when revolving at 3,500 RPM, a large rotor with a radius of 15 cm will produce a maximum G-Force of 2,058 xg while a small rotor with a radius of 5 cm will produce a maximum G-Force of 686 xg.

If you prefer to use a Nomograph to calculate your RPM or G-Force, one is provided below. Once you know what G-Forces you need to spin your samples at, you can measure the radius of your centrifuge rotor and calculate the RPM you need using the equations provided above or by using the Nomograph found below.

You may also use the equations provided above if you prefer to use the equations to the Nomograph.

In summary, you should always set your centrifuge to the correct G-Force, not by an assumed RPM. Most clinical tube manufacturers will provide Instructions for Use that specifies the recommended G-Force for their tubes. For your convenience, you can find the I.F.U. for the most common brands here.

Some centrifuges will use a display to present RPM and G-Force. In this case, you can easily set the centrifuge by G-Force without doing the calculations. If you are using a centrifuge that does not display G-Force and you are executing a protocol with one or more G-Force requirements, you will need to calculate the RPM that achieves the required G-Forces and set the centrifuge by the RPM display.