Calculator
Calculated output details
Submit the form to view converted radius values, derived motion variables, and export-ready calculation details.
Plotly graph
Calculate a radius to generate the RPM versus RCF and tip-speed graph.
Formula used
This calculator supports three radius-solving methods, depending on the values you already know from a rotor specification sheet or lab procedure.
- From RCF and RPM: r(cm) = RCF / (1.118 × 10-5 × RPM²)
- From acceleration and RPM: r = a / ω²
- From tangential speed and RPM: r = v / ω
- Angular velocity relation: ω = 2π × RPM / 60
Use the effective sample radius, measured from the rotor axis to the sample position, instead of the outer housing dimension.
How to use this calculator
- Select the calculation mode that matches your known data.
- Enter rotor RPM and the matching physical input value.
- Choose the output unit and preferred decimal precision.
- Press Calculate Radius to view results above the form.
- Download CSV or PDF after calculation for reporting.
Example data table
| Mode | Input values | Calculated radius | Notes |
|---|---|---|---|
| RCF and RPM | RCF = 5,000 ×g, RPM = 6,000 | 12.423 cm | Common rotor geometry check for separation planning. |
| RCF and RPM | RCF = 12,000 ×g, RPM = 9,000 | 13.251 cm | Higher force still stays in a realistic bench rotor range. |
| Acceleration and RPM | a = 120,000 m/s², RPM = 9,000 | 13.509 cm | Useful when acceleration is already documented in SI form. |
| Speed and RPM | v = 60 m/s, RPM = 4,500 | 12.732 cm | Back-solves radius from measured or published rim speed. |
FAQs
1. What does centrifuge radius mean here?
It is the effective distance from the rotation axis to the sample position. That distance controls centrifugal acceleration and relative centrifugal force during spinning.
2. Why does the calculator ask for RPM?
RPM determines angular velocity. Since centrifugal acceleration depends on ω², even small RPM changes can strongly affect the radius result or the force generated.
3. When should I use the RCF method?
Use it when a protocol lists target RCF and operating RPM. It is the fastest route when working from centrifuge method sheets or manufacturer force charts.
4. Can I use rotor diameter instead of radius?
Yes, but convert diameter to radius first by dividing by two. This calculator also returns rotor diameter after solving the radius.
5. Which radius should I measure on a swing rotor?
Use the effective radius to the sample location during operation. For swing-out systems, that usually means the distance at the running position rather than the parked angle.
6. Why are centrifuge formulas often written with centimeters?
Many laboratory RCF tables use a constant that expects radius in centimeters. This file converts units automatically, then still reports all major radius formats.
7. What if my result looks too small or too large?
Check RPM, unit selection, and whether acceleration or speed was entered in the correct unit. A wrong unit is the most common reason for unrealistic rotor geometry.
8. What does the graph help me see?
It shows how the solved radius would behave across a wider RPM range. That helps you compare force growth with speed growth before choosing an operating point.