RPM to RCF (×g) calculator for centrifuges
Maintained by the Talindrew team · Last updated
Relative centrifugal force depends on rotor speed and radius: RCF (×g) = 1.118 × 10⁻⁵ × r(cm) × RPM². At a 10 cm radius, 4,000 RPM is about 1,790 ×g. Protocols specify ×g because it is rotor-independent: the same RPM produces different forces in different rotors.
Result
RCF = 1.118×10⁻⁵ × r(cm) × RPM². Protocols specify ×g because it is rotor-independent, always convert through your rotor's maximum radius (printed on the rotor or its datasheet).
Keep this calculation and use it on a real construct
Free account. You land on this calculator with your numbers already filled in, next to your sequences, cloning wizards and lab notebook.
What it looks like
Formula
RCF = 1.118 × 10⁻⁵ × r (cm) × RPM² · RPM = √(RCF / (1.118 × 10⁻⁵ × r))
Source: Standard centrifugation nomogram relation (Sigma-Aldrich / Eppendorf rotor documentation)
Worked example
Given: Microcentrifuge rotor, 10 cm maximum radius, spun at 4,000 RPM
- 1.RCF = 1.118 × 10⁻⁵ × 10 × 4,000² = 1.118 × 10⁻⁴ × 1.6 × 10⁷ = 1,789 ×g.
4,000 RPM at r = 10 cm ≈ 1,790 ×g
How the calculation flows
Units & constants
| Pellet bacteria | 3,000–5,000 ×g, 10–15 min |
|---|---|
| Pellet mammalian cells | 200–300 ×g, 5 min (harder spins damage them) |
| Plasmid miniprep lysate | ≥ 12,000 ×g |
| Ethanol-precipitated DNA | ≥ 14,000 ×g, 4 °C |
| Radius to use | r_max printed on the rotor (r_min/r_avg for gradients) |
| Price | Free |
What is 1,000 ×g in RPM? ×g to RPM chart
| Force | r = 6 cm | r = 8.4 cm | r = 10 cm | r = 15 cm | r = 20 cm |
|---|---|---|---|---|---|
| 100 ×g | 1,220 | 1,030 | 950 | 770 | 670 |
| 200 ×g | 1,730 | 1,460 | 1,340 | 1,090 | 950 |
| 300 ×g | 2,110 | 1,790 | 1,640 | 1,340 | 1,160 |
| 500 ×g | 2,730 | 2,310 | 2,110 | 1,730 | 1,500 |
| 1,000 ×g | 3,860 | 3,260 | 2,990 | 2,440 | 2,110 |
| 1,500 ×g | 4,730 | 4,000 | 3,660 | 2,990 | 2,590 |
| 2,000 ×g | 5,460 | 4,610 | 4,230 | 3,450 | 2,990 |
| 3,000 ×g | 6,690 | 5,650 | 5,180 | 4,230 | 3,660 |
| 4,000 ×g | 7,720 | 6,530 | 5,980 | 4,880 | 4,230 |
| 5,000 ×g | 8,630 | 7,300 | 6,690 | 5,460 | 4,730 |
| 10,000 ×g | 12,210 | 10,320 | 9,460 | 7,720 | 6,690 |
| 12,000 ×g | 13,380 | 11,300 | 10,360 | 8,460 | 7,330 |
| 14,000 ×g | 14,450 | 12,210 | 11,190 | 9,140 | 7,910 |
| 16,000 ×g | 15,440 | 13,050 | 11,960 | 9,770 | 8,460 |
| 20,000 ×g | 17,270 | 14,590 | 13,380 | 10,920 | 9,460 |
RPM = √(RCF / (1.118 × 10⁻⁵ × r)), rounded to the nearest 10 RPM. Use r_max from your rotor's datasheet; the calculator above takes any radius.
What is 4,000 RPM in ×g? RPM to ×g chart
| Speed | r = 6 cm | r = 8.4 cm | r = 10 cm | r = 15 cm | r = 20 cm |
|---|---|---|---|---|---|
| 500 RPM | 16.8 ×g | 23.5 ×g | 27.9 ×g | 41.9 ×g | 55.9 ×g |
| 1,000 RPM | 67.1 ×g | 93.9 ×g | 112 ×g | 168 ×g | 224 ×g |
| 1,500 RPM | 151 ×g | 211 ×g | 252 ×g | 377 ×g | 503 ×g |
| 2,000 RPM | 268 ×g | 376 ×g | 447 ×g | 671 ×g | 894 ×g |
| 3,000 RPM | 604 ×g | 845 ×g | 1,010 ×g | 1,510 ×g | 2,010 ×g |
| 4,000 RPM | 1,070 ×g | 1,500 ×g | 1,790 ×g | 2,680 ×g | 3,580 ×g |
| 5,000 RPM | 1,680 ×g | 2,350 ×g | 2,790 ×g | 4,190 ×g | 5,590 ×g |
| 6,000 RPM | 2,410 ×g | 3,380 ×g | 4,020 ×g | 6,040 ×g | 8,050 ×g |
| 8,000 RPM | 4,290 ×g | 6,010 ×g | 7,160 ×g | 10,700 ×g | 14,300 ×g |
| 10,000 RPM | 6,710 ×g | 9,390 ×g | 11,200 ×g | 16,800 ×g | 22,400 ×g |
| 12,000 RPM | 9,660 ×g | 13,500 ×g | 16,100 ×g | 24,100 ×g | 32,200 ×g |
| 13,000 RPM | 11,300 ×g | 15,900 ×g | 18,900 ×g | 28,300 ×g | 37,800 ×g |
| 14,000 RPM | 13,100 ×g | 18,400 ×g | 21,900 ×g | 32,900 ×g | 43,800 ×g |
| 15,000 RPM | 15,100 ×g | 21,100 ×g | 25,200 ×g | 37,700 ×g | 50,300 ×g |
RCF = 1.118 × 10⁻⁵ × r × RPM², three significant figures. Force grows with the square of speed: doubling RPM quadruples ×g.
Why do protocols say ×g instead of RPM?
Because RPM is meaningless without the rotor. 4,000 RPM is 1,790 ×g in a 10 cm rotor but 2,680 ×g in a 15 cm one, a 50% difference that decides whether mammalian cells survive the spin. Force in ×g transfers between machines; converting it to your rotor's RPM is the one step this calculator does.
Which radius do you plug in?
The maximum radius (r_max), the distance from the axis to the bottom of the tube, for pelleting, which is where the pellet forms and where vendors define their rotor's rating. Density-gradient work sometimes quotes r_avg because the force varies along the tube; your rotor's datasheet lists all three.
Frequently asked questions
It depends on the rotor radius: 1,000 ×g is 2,990 RPM at a 10 cm radius, 3,260 RPM at 8.4 cm (a typical microcentrifuge) and 2,440 RPM at 15 cm. RPM = √(1,000 / (1.118 × 10⁻⁵ × r)).
300 ×g is 1,640 RPM at a 10 cm radius, 1,340 RPM at 15 cm and 1,160 RPM at 20 cm, the range of most benchtop swing-bucket rotors. Spin 5 minutes; harder spins compact and damage cells.
Use RCF = 11.18 × r(cm) × (RPM / 1,000)². For 4,000 RPM at a 10 cm radius: 11.18 × 10 × 4² = 1,789 ×g. It is the same formula as 1.118 × 10⁻⁵ × r × RPM² with the RPM written out in full.
For the common ~8.4 cm-radius fixed-angle rotor: 1.118 × 10⁻⁵ × 8.4 × 13,000² ≈ 15,900 ×g, which is why 'max speed' minipreps quote ~16,000 ×g. Your rotor's exact radius shifts this.
The formula uses radius only; the rotor's angle is already reflected in where r_max falls. Just read r_max from the rotor's spec rather than measuring the tube.
Related calculators & guides
Use this calculator inside the app
Free to use. No download required. Sign in and you land right back on this calculator.