rpm to RCF (×g) Converter for Centrifuges
Convert rpm to RCF (×g) for Centrifuges
Convert centrifuge speed from rpm to relative centrifugal force (×g) or back. Enter the rotor radius, then rpm or ×g. Joan Lab LC500 rotor presets are included.
What is rpm?
rpm (revolutions per minute) measures rotational speed. On a centrifuge rpm alone is not enough, because the force on the sample also depends on its distance from the axis.
What is RCF (×g)?
RCF (relative centrifugal force) compares the centrifugal force with Earth gravity. 1000 ×g means the sample feels 1000 times its own weight. Separation protocols are written in this unit.
rpm to RCF formula
The constant 1.118 × 10⁻⁵ is (2π ÷ 60)² ÷ 980.665 cm/s², so the formula is simply RCF = ω²r ÷ g.
Quick table: rpm to ×g
Rounded RCF values for common rotor radii.
| rpm | r = 5 cm | r = 8 cm | r = 10 cm | r = 12 cm | r = 15 cm |
|---|---|---|---|---|---|
| 500 | 14 | 22 | 28 | 34 | 42 |
| 1,000 | 56 | 89 | 112 | 134 | 168 |
| 1,500 | 126 | 201 | 252 | 302 | 377 |
| 2,000 | 224 | 358 | 447 | 537 | 671 |
| 3,000 | 503 | 805 | 1,006 | 1,207 | 1,509 |
| 4,000 | 894 | 1,431 | 1,789 | 2,147 | 2,683 |
| 5,000 | 1,397 | 2,236 | 2,795 | 3,354 | 4,192 |
| 10,000 | 5,590 | 8,944 | 11,180 | 13,416 | 16,770 |
| 12,000 | 8,050 | 12,879 | 16,099 | 19,319 | 24,149 |
| 15,000 | 12,577 | 20,124 | 25,155 | 30,186 | 37,732 |
Worked examples
Example 1: rpm to RCF
A centrifuge runs at 3000 rpm with a 10 cm rotor radius. What is the RCF?
- RCF = 1.118 × 10⁻⁵ × 10 × 3000²
- RCF = 1006
Answer: about 1006 ×g.
Example 2: protocol ×g to rpm
A protocol asks for 1500 ×g on a Joan Lab LC500-6 (r = 12 cm). What rpm do you set?
- rpm = √(1500 ÷ (1.118 × 10⁻⁵ × 12))
- rpm ≈ 3,344
Answer: about 3,344 rpm, below the 4000 rpm limit.
Example 3: changing rotors
Old protocol: 4000 rpm at r = 8 cm. New rotor r = 12 cm. What rpm gives the same ×g?
- Old RCF = 1.118 × 10⁻⁵ × 8 × 4000² = 1431 ×g
- New rpm = √(1431 ÷ (1.118 × 10⁻⁵ × 12)) = 3266
Answer: about 3270 rpm.
r max, r min or r average?
The tube bottom (r max) sees the highest force and the tube mouth (r min) the lowest. Protocols usually use r max. Swing-out rotors have a larger r max when spinning; fixed-angle rotors keep the same radius.
Centrifuges and accessories at AMI Scientific
The Joan Lab and DLAB centrifuges and Iwaki tubes below are available at AMI Scientific. Maximum ×g values are from the product specifications.
Frequently asked questions
What is rpm?
rpm (revolutions per minute) is the number of full turns per minute. 3000 rpm means 3000 turns a minute, or 50 per second.
What is the difference between rpm and RCF (×g)?
rpm is only rotational speed. RCF is the force the sample feels, as a multiple of Earth gravity. It depends on both rpm and rotor radius, so the same rpm gives less force in a smaller rotor.
Why do protocols use ×g instead of rpm?
Because ×g is reproducible on any centrifuge. An rpm value only matches if the rotor radius is the same.
How do I find my rotor radius?
Check the rotor manual or label for r max in mm or cm. Otherwise measure from the spindle centre to the tube bottom in the spinning position.
Is RCF the same as g-force?
Yes. RCF (relative centrifugal force), g-force and ×g all refer to the same quantity.
Looking for a lab centrifuge?
Joan Lab LC500 benchtop centrifuges (up to 4000 rpm, about 2100 ×g) and high-speed micro centrifuges are available at AMI Scientific, with formal quotations and tax invoices.
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