Acceleration Calculator
Calculate acceleration from velocity change and time, force and mass, or centripetal motion. Convert between m/s², g-force, ft/s², and more.
Centrifuge Speed Calculator
Convert between RPM and RCF (× g) for centrifuges. Calculate required RPM from g-force or compute RCF from speed and rotor radius.
Centrifuge Speed Calculator
rev/min
Distance from rotor center to sample
cm
RCF (× g)⧉
1,409
1,409 times gravitational acceleration
RPM⧉
3,000
50.0 revolutions per second
Rotor Radius⧉
14.0 cm
0.1400 m
Angular Velocity⧉
314.2 rad/s
Period: 20.0 ms per revolution
Tip Speed⧉
44.0 m/s
158.3 km/h tip velocity
Force Category⧉
High Speed
Organelle isolation, DNA prep
RCF Scale (log)
1×g100×g10,000×g1,000,000×g
RPM ↔ RCF Conversion Table
| RPM | RCF at 14.0 cm | Category |
|---|---|---|
| 500 | 39 × g | Low |
| 1,000 | 157 × g | Low |
| 2,000 | 626 × g | High |
| 3,000 | 1,409 × g | High |
| 5,000 | 3,913 × g | High |
| 8,000 | 10,017 × g | High |
| 10,000 | 15,652 × g | High |
| 14,000 | 30,678 × g | Very High |
| 20,000 | 62,608 × g | Very High |
| 40,000 | 250,432 × g | Ultra |
Common Lab Protocols
| Protocol | RCF (× g) | Time (min) | RPM at 14.0 cm |
|---|---|---|---|
| Blood serum separation | 1,500 | 10 | 3,096 |
| Cell pellet (mammalian) | 300 | 5 | 1,384 |
| Bacteria pellet | 5,000 | 10 | 5,652 |
| Mitochondria isolation | 10,000 | 10 | 7,993 |
| DNA ethanol precipitation | 16,000 | 15 | 10,111 |
| Microsome isolation | 100,000 | 60 | 25,276 |
| Ribosome pelleting | 150,000 | 120 | 30,957 |
Planning notes, formulas, and examples
About the Centrifuge Speed Calculator
Centrifuge speed is usually shown as RPM, but lab protocols are often written in RCF, or relative centrifugal force, which is the actual acceleration experienced by the sample. Converting between the two depends on rotor radius, so the same protocol can require different RPM on different machines.
This calculator converts between RPM, RCF, and rotor radius using the standard relationship RCF = 1.118 × 10^-5 × r × RPM^2. Enter the values you know, choose what you want to solve for, and it will return the matching centrifuge settings.
Protocol presets and reference tables make it easier to translate a published RCF into the RPM your rotor needs, or to see how strongly a given spin will act on the sample.
When This Page Helps
Centrifuge protocols are easy to misapply when the paper reports RCF but the instrument shows RPM. The radius of the rotor changes the actual force, so a correct conversion is the difference between a usable separation and a spin that is too weak or too aggressive.
Putting RPM, RCF, and rotor radius on the same page helps with protocol transfer, rotor selection, and quick checks before you run a sample.
How to Use the Inputs
- Choose what to solve for: RCF from RPM, RPM from RCF, or radius from both.
- Enter the known values (RPM, RCF, and/or rotor radius in cm).
- Use rotor preset buttons to quickly set common rotor radii.
- Read the converted value and additional results.
- Check the protocol table for RPM equivalents at your rotor radius.
- Use protocol presets (Cell Pellet, DNA Prep, etc.) to look up standard settings.
Formula used
RCF = 1.118 × 10⁻⁵ × r × RPM². RPM = √(RCF / (1.118 × 10⁻⁵ × r)). r = RCF / (1.118 × 10⁻⁵ × RPM²). Where r is the rotor radius in centimeters.Example Calculation
Result: 1,413 × g
At 3,000 RPM with a swinging-bucket rotor (14.0 cm radius), the sample experiences 1,413 times gravitational acceleration. This is suitable for cell pelleting and serum separation protocols.
Tips & Best Practices
- Always measure radius to the bottom of the tube, not the middle — the maximum radius determines effective g-force.
- RCF at the top of the tube is lower than at the bottom for fixed-angle rotors; use maximum radius.
- For swinging-bucket rotors, radius changes during acceleration — use the fully-swung-out radius.
- Write "× g" or "RCF" in your lab notebook, never "RPM" alone, so protocols are transferable.
- Ultracentrifuge rotors have specific speed limits — never exceed the rated maximum RPM.
- Temperature affects separations more than small RCF variations — keep temp controlled.
Differential Centrifugation
Differential centrifugation separates cellular components by successive spins at increasing g-force. The first spin at 300 × g pellets intact cells but leaves organelles in the supernatant. The 10,000 × g spin pellets mitochondria and lysosomes. The 100,000 × g ultracentrifuge spin brings down microsomes and ribosomes.
Fixed-Angle vs. Swinging-Bucket Rotors
Fixed-angle rotors pellet particles against the tube wall, resulting in faster sedimentation but compacted pellets. Swinging-bucket rotors pellet to the tube bottom, producing loose pellets ideal for gradient separations. The effective radius is different for each type.
Density Gradient Centrifugation
Sucrose, cesium chloride, or Percoll gradients allow separation by density rather than just size. Isopycnic (equilibrium) centrifugation spins samples long enough that particles band at their buoyant density. Rate-zonal centrifugation separates by sedimentation rate in a short spin.
Sources & Methodology
Last updated:
Frequently Asked Questions
RCF describes the actual force on the sample, which determines separation effectiveness. Different centrifuges with different rotor radii need different RPM to achieve the same RCF, making RPM non-transferable between instruments.
Measure from the center of the rotor (axis of rotation) to the bottom of the sample tube or the furthest point the sample reaches. Check your rotor manual for the exact specification — it varies between fixed-angle and swinging-bucket designs.
RCF (relative centrifugal force) and × g are the same thing: a dimensionless ratio comparing centrifugal acceleration to gravitational acceleration (9.81 m/s²). "300 × g" and "RCF 300" are interchangeable.
The squared relationship means small RPM changes have large effects on g-force. Increasing from 3,000 to 4,000 RPM (33% increase) raises g-force by 78%. This is why accurate RPM is critical for reproducible separations.
Only if your centrifuge can handle that RPM safely. Always check maximum RPM ratings for your specific rotor. Using a smaller-radius rotor requires higher RPM for the same RCF, which may exceed limits.
The k factor is a measure of pelleting efficiency that accounts for rotor geometry. A lower k factor means faster pelleting. It is calculated from the maximum and minimum radii and the maximum RPM of the rotor.
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