Convert a centrifuge's RPM to ×g (RCF)

Protocols specify 10,000 ×g, but the centrifuge dial says RPM. The rotor radius links them — convert properly.

Tools used in this guide

RPM ↔ RCF calculator
Half-life calculator
Molar mass calculator

The job

RCF — the actual force on the sample — depends on both speed and rotor radius. Two rotors at the same RPM can differ by 30% in g-force, which is why protocols specify ×g, not RPM.

Radius plus one number

Measure (or look up) the rotor radius to the tube bottom at full swing-out, in cm. Enter RPM to get RCF, or RCF to get the RPM to dial in.

Worked example: r = 8 cm at 10,000 RPM → ≈8,944 ×g.
A '10,000 ×g' protocol on that rotor needs about 10,580 RPM.

Check the rotor spec

Radius conventions differ — some manuals quote r_max (tube bottom), others r_av. The tool uses whatever radius you enter, so use the manual's number for the position your protocol means.