Drybench Calc.
Centrifuge RCF and RPM conversion
Relative centrifugal force from rotor speed and radius, or the speed for a force, with the radius convention stated and the published rounded coefficient.
RCF and RPM
Use measured inputs and your protocol’s targets. Save the exact setup or export a free preparation sheet.
Radius is the distance from the rotation axis to the specified sample position. Check that your protocol uses the same radius convention. No centrifugation time or rotor certification is supplied.
Answer
1,956.5 × g at 5,000 RPM, 7 cm maximum radius.
- Relative centrifugal force
- 1,956.5× g
- Rotor radius
- 7cm
Planned calculation; no performed preparation is recorded.
Calculated setup
| Quantity or basis | Value |
|---|---|
| Rotor speed | 5,000 RPM |
| Relative centrifugal force | 1,956.5 × g |
| Rotor radius | 7 cm |
| Radius convention | maximum |
| Published coefficient | 1.118E-5 cm⁻¹ RPM⁻² |
- Calculated setup only; this is not a performed preparation or measurement.
- RCF = 1.118 × 10⁻⁵ × radius in cm × RPM², using the published rounded coefficient. Radius runs from the axis to the stated sample position. This conversion does not certify rotor limits or supply a centrifugation time.
Illustrative arithmetic only; no biological target or equipment setting is recommended.
Assumptions and qualifications
Open in the bench sheetThe bench sheet carries these inputs and offers the other calculators.
Worked example
- 7 cm at 5,000 RPM, maximum radius: RCF = 1.118 × 10⁻⁵ × 7 × 5,000² = 1,956.5 × g.
- The inverse: 1,956.5 × g at 7 cm is 5,000 RPM. The same radius typed as 70 mm gives the same answers.
- 1.118 × 10⁻⁵ is the published rounded value of (2π/60)² ÷ gₙ, 0.022 percent below the exact value; the result names the radius, its unit and its convention, so a change of convention changes the record.
- No centrifugation time or rotor limit is supplied. A rotor maximum you type is checked against the converted speed, never assumed.
Method
- Centrifugal force from rotor speed and radius. RCF = 1.118 × 10⁻⁵ × r(cm) × RPM², the published rounded coefficient (Thermo Fisher TR0040.1, read 10 October 2026).Checked against exact rational arithmetic (Python 3.13.16 fractions and decimal) on 10 cases, three of them refusals, to nine significant figures; the rounded coefficient is within 0.03% of (2π/60)²/gₙ (10 October 2026).
Limits
- For research and education only, and not medical advice: the stock, dilution and buffer calculations here are not for dosing or clinical preparation.
- RCF and RPM convert with the published rounded coefficient 1.118 × 10⁻⁵ and the radius you supply; no centrifugation time, rotor model or rotor limit is supplied or certified.