Centrifuge RPM Calculator
Centrifuge RCF and tip speed from radius and rpm.
What it does
Centrifuges rate force in g: radius times speed squared times a constant. Double rpm quadruples g while double radius only doubles it, which is why speed rules protocols. This page reports RCF with tip speed beside it.
The default is 10 cm at 5,000 rpm. RCF is 2,795 xg with tip speed 52.4 m/s. Dropping to 3,000 rpm cuts force to 1,006 xg since the square bites.
Radius means max: tube bottom, not middle or cap. Fixed angle and swinging buckets swing different radii at the same rpm, so read the rotor card for the right centimeter.
Force is not permission. Tube max g, rotor max rpm, balance within grams, and sealed aerosol handling all gate the run before math matters.
How to use
- Enter max radius in cm.
- Enter rotor speed in rpm.
- Read RCF first.
- Read tip speed next.
- Check tube and rotor ratings.
Formula
- radius
- Max radius to tube bottom.
- rpm
- Rotor speed per minute.
Radius is max (tube bottom) in cm; RCF reports average only at that radius. The constant folds Earth g with unit changes. Tubes, buckets, and rotors carry max ratings that beat any calculation.
Worked example
Example: benchtop spin
10 cm radius at 5,000 rpm.
- Square: 5,000^2 = 25,000,000.
- RCF: 1.118e-5 x 10 x 25,000,000 = 2,795 xg.
- Tip: 5,000 x 2 x 3.1416 / 60 x 0.1 = 52.4 m/s.
- Check: RCF rises with the square of rpm.
- Tool shows 2,795 xg and 52.4 m/s.
Reference table
| RPM | RCF | Tip m/s |
|---|---|---|
| 1,000 | 112 xg | 10.5 |
| 3,000 | 1,006 xg | 31.4 |
| 5,000 | 2,795 xg | 52.4 |
| 10,000 | 11,180 xg | 104.7 |
| 20,000 | 44,720 xg | 209.4 |
Limits
- Force only. No time or pelleting.
- Max radius assumed. Gradients vary.
- Ratings, balance, aerosols excluded.
- One radius per pass.
Common mistakes
- Using average radius as max.
- Reading rpm as RCF.
- Scaling force linearly with rpm.
- Mixing cm with mm.
- Running past tube ratings.
Try it yourself
Quick checks. Answers sit tucked under each question.
10 cm at 3,000 rpm?
1,006 xg (1.118e-5 x 10 x 9,000,000).
10 cm at 10,000 rpm?
11,180 xg (1.118e-5 x 10 x 100,000,000).
Questions
RCF?
1.118e-5 times cm times rpm squared. Here 2,795 xg.
Tip speed?
RPM times 2 pi over 60 times meters. Here 52.4 m/s.
10 cm at 3,000 rpm?
1,006 xg with tip 31.4 m/s.
Which radius?
Radius to tube bottom, the max radius.
Safe to run?
No. Tube rating, balance, and aerosols rule real runs.
Pellet time?
No. Time and braking sit outside force math.