How to use (3 steps)
- Pick an example or choose a mode (rpm → ×g / ×g → rpm).
- Confirm the radius (distance from rotor center to sample) and unit (mm/cm/in).
- Enter rpm or ×g to see the converted result.
RCF depends on how radius is defined (rmax/ravg, etc.). Use the value provided in your rotor manual if possible.
Quick protocol workflow (when switching centrifuges)
- Convert the original protocol rpm to RCF (×g) using the original rotor radius.
- Keep that target RCF, then convert back to rpm with your destination rotor radius.
- Record both the radius definition and units (mm/cm/in) in your note so the run can be reproduced.
This keeps force level consistent across rotors better than copying rpm alone.
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Input (radius, rpm/RCF)
Result (conversion)
Source RCF result
Theoretical rpm
Instrument setting rpm
RCF at the setting
Difference
Source radius definition → Destination radius definition
×g (RCF)
14,170.65
Radius: 7.5 cm / rpm: 13,000 rpm
Static sample uses r=7.5 cm and 13,000 rpm. Use the rotor manual's rmax/ravg definition consistently; JavaScript recalculates this block from your inputs.
| rpm | ×g (RCF) |
|---|---|
| 1,000 | 83.85 |
| 3,000 | 754.65 |
| 5,000 | 2,096.25 |
| 8,000 | 5,366.40 |
| 10,000 | 8,385.00 |
| 13,000 | 14,170.65 |
| 15,000 | 18,866.25 |
Formula used (coefficient 1.118×10^-5)
RCF(×g) = 1.118×10^-5 × r(cm) × rpm^2 rpm = sqrt( RCF / (1.118×10^-5 × r(cm)) ) r(cm) = r(mm) / 10 r(cm) = r(inch) × 2.54
Share
The share URL stores mode, radius, radius definition, unit, the active rpm or ×g value, and table visibility. No values are sent to a server.
How it’s calculated
This tool converts radius to cm and uses a commonly used formula.
- RCF(×g) = 1.118×10^-5 × r(cm) × rpm²
- rpm = √( RCF / (1.118×10^-5 × r(cm)) )
RCF depends on how radius is defined (rmax/ravg, etc.). If results look off, recheck units (mm/cm/in) and your radius definition.
FAQ
What is RCF (×g)?
It is the relative centrifugal force expressed as a multiple of gravitational acceleration (g). Protocols often use ×g to compare conditions across different centrifuges and rotors.
Which radius should I use?
Maximum RCF is normally based on rmax. We do not recommend ravg as a safety default; use the definition in your rotor manual. An adapter can change the effective radius, and matching RCF alone does not automatically make time, braking, or sample conditions equivalent.
Should I use rmax or ravg?
Use the definition stated in your protocol and rotor manual. If the definition is unclear, do not assume ravg is a safe default. You can keep the original rpm with the same rotor, but for another rotor, confirm the radius definition and compare using RCF.
How do I reproduce an rpm protocol on a different centrifuge?
RCF changes with radius even at the same rpm. Convert the original rpm to ×g first, then convert ×g back to rpm using your rotor radius.
Why does my result differ from other sites?
Differences can come from constants, the definition of g, and how radius is defined (cm/mm, rmax/ravg). This tool uses a common formula with radius in cm.
Can I enter 0 rpm or 0 ×g?
Yes. Entering 0 gives 0 as the result (radius must be non-zero).
Why does the result feel too strong or too weak?
Common causes are unit mistakes (mm vs cm) and radius definition differences. Recheck units and radius.
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