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RCF or × g
Relative centrifugal force describes the acceleration acting on the sample at the selected radius. It is expressed as × g.
Lab calculator · RCF · RPM · rotor radius
Convert RCF and RPM for centrifuges
The calculator converts RCF to RPM or RPM to RCF Two values are required: centrifugal force or rotational speed, plus the maximum rotor radius.
Direct answer
Enter the rotor radius in millimetres and the known starting value. The result is calculated locally in your browser immediately. For technically transferring a protocol, RCF or the × g value is more meaningful than RPM alone.
- RCF → RPM
- RPM → RCF
- Radius in mm
- Copy result
- No data transmission
2 directionsRCF to RPM and RPM to RCF
rmaxAxis of rotation to tube bottom
1.118 × 10⁻⁵Formula constant with radius in cm
localCalculation directly in the browser
Interactive calculator
Calculate centrifugal force or rotational speed
Select the calculation direction and enter two values. Decimal values are supported.
Revolutions per minute
RPM
Axis of rotation to tube bottom
mm
Insert radius quickly
Result
Calculated relative centrifugal force
Relative centrifugal force
× g
Axis of rotation to tube bottom
mm
Insert radius quickly
Result
Required RPM for the selected RCF
The calculator performs a mathematical conversion. Approved specifications from the tube and centrifuge manufacturers remain authoritative.
Distinguish the terms clearly
What do RCF and RPM mean?
RCF and RPM do not describe the same thing. RCF indicates the relative centrifugal force acting on the sample as a multiple of gravitational acceleration. RPM describes only the rotor speed.
Key ruleThe same RPM does not automatically mean the same × g when rotor radii differ.
RPM
RPM stands for revolutions per minute. It describes the rotor speed but does not take the rotor radius into account.
Rotor radius rmax
For this calculator, use the distance from the axis of rotation to the bottom of the inserted tube in its operating position.
Why is RCF more important when transferring a protocol?
A protocol that specifies only RPM cannot be transferred unambiguously to another device without the radius. RCF combines rotational speed with the actual radius.
Determine rmax correctly
Which rotor radius should be entered?
Use the maximum rotor radius: the distance from the axis of rotation to the bottom of the tube with the rotor, adapter and tube positioned exactly as during operation.
Do not estimateThe value can change depending on the rotor, adapter, tube length and operating position.
1
Check the instructions Device or rotor documentation is the primary source.
2
Use the actual setup Rotor, adapter and tube must match the actual operating setup.
3
Measure to the tube bottom Do not measure to the upper edge of the rotor or adapter.
Important: Do not use a radius from another centrifuge model or a different adapter without verifying it.
Mathematical basis
Convert RCF to RPM and RPM to RCF
The formula uses the rotor radius in centimetres. The calculator accepts the value in millimetres and internally divides it by ten.
Check the unitIn the formula, 86 mm equals 8.6 cm.
Convert RPM to × g
RCF = 1.118 × 10⁻⁵ × r(cm) × RPM²
Rotational speed and rotor radius are known. The relative centrifugal force is calculated.
Convert × g to RPM
RPM = √[RCF ÷ (1.118 × 10⁻⁵ × r(cm))]
Target RCF and rotor radius are known. The required rotational speed is calculated.
Common calculation queries
Typical RCF/RPM calculation examples
The tables show purely mathematical examples. They do not define a protocol and do not replace device approval or manufacturer instructions.
Rule of thumbWith the same target RCF, a smaller radius requires a higher rotational speed.
Example 01
Convert 1000 × g to RPM
| Rotor radius | Calculated RPM |
|---|---|
| 50 mm | approx. 4230 RPM |
| 86 mm | approx. 3225 RPM |
| 100 mm | approx. 2991 RPM |
Example 02
Convert 1200 × g to RPM
| Rotor radius | Calculated RPM |
|---|---|
| 50 mm | approx. 4633 RPM |
| 65 mm | approx. 4064 RPM |
| 85 mm | approx. 3554 RPM |
| 86 mm | approx. 3533 RPM |
| 100 mm | approx. 3276 RPM |
| 110 mm | approx. 3124 RPM |
Example 03
Convert 3500 RPM to × g
| Rotor radius | Calculated RCF |
|---|---|
| 50 mm | approx. 685 × g |
| 86 mm | approx. 1178 × g |
| 100 mm | approx. 1370 × g |
Example 04
What does 300 × g mean in a centrifuge?
300 × g describes an acceleration that is mathematically 300 times gravitational acceleration. The corresponding RPM depends on the rotor radius. At a radius of 86 mm, approximately 1766 RPM would be required.
Manufacturer-specific standard protocol
Vi PRP-PRO: 1200 × g for 7 minutes
For preparation with Vi PRP-PRO PRP tubes the standard centrifugation protocol is 1200 × g with a run time of 7 minutes. The required RPM is calculated from the actual rotor radius of the centrifuge used.
1200× g
7 minutes
The calculated RPM values are mathematically rounded. Use only settings supported by the centrifuge, rotor, adapter and tube system.
Check before starting
Technically transfer a centrifugation protocol
Converting RCF and RPM is only one part of the process. Other parameters can affect transferability.
Calculator limitationMathematically equivalent does not automatically mean technically or regulatorily approved.
Target RCF and run time
Use all approved specifications of the tube system.
Rotor and adapter
Check rotor type, actual radius, adapter and tube position.
Device limits
Observe permitted RPM, RCF, loading and compatible vessels.
Acceleration and braking
Do not omit specifications for acceleration ramps, braking behaviour and temperature.
Load symmetrically
Follow the manufacturer specifications for balancing and counterloading.
Responsible approval
Validated internal work instructions and manufacturer documents remain authoritative.
Technical note: The calculator does not provide medical advice or an independent centrifugation protocol. It mathematically converts known technical values.
Related technical pages
Check the tube system and centrifuge together
The conversion is only meaningful when target RCF, rotor, adapter, vessel and device limits are compatible.
WorkflowProtocol value → rotor radius → RPM → device approval.
Quick answers
Frequently asked questions about the RCF/RPM calculator
How can I convert RCF to RPM?
Enter the target RCF and maximum rotor radius. The calculator uses the formula RPM = √[RCF ÷ (1.118 × 10⁻⁵ × r(cm))].
How can I convert RPM to RCF or × g?
Enter the RPM and maximum rotor radius. The calculator uses the formula RCF = 1.118 × 10⁻⁵ × r(cm) × RPM².
Why is RPM alone not enough?
The RCF acting on the sample depends on both rotational speed and rotor radius. Two centrifuges can therefore generate different × g values at the same RPM.
Which rotor radius should I use?
Use rmax: the distance from the axis of rotation to the bottom of the inserted tube in its operating position. The rotor and adapter must match the actual setup used.
How many RPM correspond to 1200 × g?
This depends on the rotor radius. At a radius of 86 mm, 1200 × g corresponds to about 3533 RPM; at 100 mm, about 3276 RPM.
What does 3500 RPM produce at an 86 mm radius?
The mathematical conversion gives approximately 1178 × g. A rounded device setting may therefore differ slightly from the calculated target value.
Can the calculator be used for PRF protocols?
The mathematical conversion is independent of the sample type. Target RCF, run time and other parameters must however be taken from the applicable validated protocol.
Why is the result rounded?
The calculator displays a rounded whole-number value. Many centrifuges can also only be set in fixed RPM increments. The usable setting must be checked against the device specifications.
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