# Centrifuge RPM to g-force (RCF) calculator

> Convert centrifuge RPM to g-force (RCF) and back for your rotor radius: RCF = 1.118 × 10⁻⁵ × r × RPM². Match a protocol on a different rotor. Free.

URL: https://www.labcanvas.com/tools/centrifuge-rpm-rcf-calculator

RCF (× g) = 1.118 × 10⁻⁵ × r × RPM², with r the rotor radius in centimetres; to go the other way, RPM = √(RCF / (1.118 × 10⁻⁵ × r)). For example, 10,000 RPM at a radius of 10 cm is 11,180 × g. Enter the speed or the g-force and the radius, or convert a protocol’s speed to the speed that gives the same g-force on your own rotor.

## Quick answer

- **What it does:** Converts centrifuge speed in RPM to relative centrifugal force (× g) and back for your rotor radius, and matches a protocol’s g-force on a different rotor.
- **Formula:** RCF = 1.118 × 10⁻⁵ × r (cm) × RPM²; RPM = √(RCF ÷ (1.118 × 10⁻⁵ × r)); RPM₂ = RPM₁ × √(r₁ ÷ r₂).
- **Example:** 10,000 RPM at a 10 cm radius: RCF = 1.118 × 10⁻⁵ × 10 × 10,000² = 11,180 × g.

Free, in the browser, no account needed. Updated 2026-11-08.

## Features

- RPM → relative centrifugal force (× g)
- × g → the RPM to set
- Match a protocol: same g-force on a rotor with a different radius
- g-force at the minimum and maximum radius of the tube
- Radius in cm or mm

## How to use it

1. **Choose the direction**: RPM to × g, × g to RPM, or match a protocol written for another centrifuge.
2. **Enter the radius**: The distance from the centre of the rotor to the sample, from the rotor’s specification or measured, in cm or mm.
3. **Enter the speed or the force**: Type the RPM or the × g; the answer updates as you type. Add the minimum and maximum radius to see the force at the top and bottom of the tube.

## At a glance

| | |
| --- | --- |
| Formula | \(\mathrm{RCF} = 1.118\times10^{-5}\) \({}\times r\,(\mathrm{cm}) \times \mathrm{RPM}^2\) |
| Solves for | RCF (× g), RPM, or the RPM for the same g-force on another rotor |
| Radius | cm or mm, from the axis to the sample; optional minimum and maximum |
| Sources | Klionsky 2026 (Autophagy); Harrison et al. 2023 (Cureus) |

## How it works

$$\mathrm{RCF} = 1.118\times10^{-5} \times r \times \mathrm{RPM}^2$$

$$\mathrm{RPM} = \sqrt{\frac{\mathrm{RCF}}{1.118\times10^{-5} \times r}}$$

$$\begin{aligned} &\text{Same g-force on another rotor:} \\ &\mathrm{RPM}_2 = \mathrm{RPM}_1 \times \sqrt{r_1 / r_2} \end{aligned}$$

where RCF is the relative centrifugal force in multiples of Earth’s gravity (× g), \(r\) the radius in centimetres from the axis of rotation to the sample and RPM the speed in revolutions per minute. This is the relation given by Klionsky ([Autophagy, 2026](https://doi.org/10.1080/15548627.2026.2685350)) and Harrison et al. ([Cureus, 2023](https://doi.org/10.7759/cureus.36099)); the calculator reproduces Harrison et al.’s worked example (1000 × g at a 9 cm radius needs 3153 RPM). Because the force grows with the square of the speed, doubling the RPM gives four times the g-force (Bains et al., [J Oral Biol Craniofac Res, 2023](https://doi.org/10.1016/j.jobcr.2023.09.003)). The third line follows from setting the two forces equal.

The force is not the same throughout a tube: it is lowest at the top (minimum radius) and highest at the bottom (maximum radius), so methods should say which radius the g-force refers to; Miron et al. propose reporting the rotor dimensions, angle, RPM and time with the RCF ([J Periodontol, 2019](https://doi.org/10.1002/JPER.18-0553)).

## Worked example

**RPM to × g.** 10,000 RPM in a rotor with a 10 cm radius: \(\mathrm{RCF} = 1.118\times10^{-5} \times 10 \times 10{,}000^2\) \(= \mathbf{11{,}180} \times g\).

**× g to RPM.** For 1000 × g at a 9 cm radius: \(\mathrm{RPM} = \sqrt{1000 / (1.118\times10^{-5} \times 9)}\) \(= \mathbf{3153\ RPM}\) (the example in Harrison et al., 2023).

**Matching a protocol.** A protocol spins at 3000 RPM in a rotor with a 15 cm radius, which is \(1.118\times10^{-5} \times 15 \times 3000^2 = 1509 \times g\). On a rotor with an 8 cm radius the same force needs \(3000 \times \sqrt{15 / 8} = \mathbf{4108\ RPM}\); running it at 3000 RPM would give only 805 × g.

## Questions

### How do I convert RPM to g (RCF)?

Multiply \(1.118\times10^{-5}\) by the rotor radius in centimetres and by the square of the RPM: \(\mathrm{RCF} = 1.118\times10^{-5} \times r \times \mathrm{RPM}^2\). At 5000 RPM and a 10 cm radius that is \(1.118\times10^{-5} \times 10 \times 25{,}000{,}000\) \(= 2795 \times g\).

### How do I convert g to RPM?

\(\mathrm{RPM} = \sqrt{\mathrm{RCF} / (1.118\times10^{-5} \times r)}\), with \(r\) in centimetres. For 1000 × g at a 9 cm radius, \(\mathrm{RPM} = \sqrt{1000 / 0.00010062} \approx 3153\).

### Is 10,000 RPM the same as 10,000 × g?

No. RPM is a speed and × g is a force, and the force depends on the radius as well. 10,000 RPM is 11,180 × g at a 10 cm radius but 5590 × g at 5 cm. Journals ask for × g, or the RPM together with the rotor, so that others can repeat the spin.

### Which radius should I use?

The distance from the centre of the rotor to the part of the sample you care about, in centimetres. The rotor’s specification usually lists it; otherwise measure it. The force is smallest at the top of the tube (minimum radius) and largest at the bottom (maximum radius), so say which one you used.

### How do I run a protocol on a centrifuge with a different rotor?

Keep the g-force, not the RPM. Work out the protocol’s × g from its speed and radius, then the RPM that gives that force on your rotor: \(\mathrm{RPM}_2 = \mathrm{RPM}_1 \times \sqrt{r_1 / r_2}\). Use the “Match a protocol” mode.

### Why does doubling the speed quadruple the force?

Because the force grows with the square of the speed: \((2 \times \mathrm{RPM})^2 = 4 \times \mathrm{RPM}^2\). Halving the radius at the same speed halves the force.