RPM from RCF calculator
A paper says spin at so many × g. This is the speed to set on your centrifuge.
Free, no account needed. Nothing you type is sent anywhere or stored — the arithmetic runs in your browser.
Inputs
Results
Speed to set (rpm)
11583
The formula
rpm = √(RCF ÷ (1.118 × 10⁻⁵ × r)), radius in centimetres. It is the g-force equation rearranged, and the square root is why halving the force does not halve the speed.
This is the conversion that matters
Methods sections quote × g precisely so the spin can be reproduced on any machine — but a centrifuge dial is in rpm, so somebody has to do this conversion at the bench, with the radius of the rotor actually in front of them.
Get the radius from the rotor manual rather than measuring the lid. It is the distance from the axis to the bottom of the tube in its spun position, and a swing-out rotor differs from a fixed-angle one of the same size.
Check the rotor will do it
A speed this gives you may be above what your rotor is rated for, especially with heavier tubes or adapters. The number here is arithmetic; the maximum on the rotor is a safety limit, and it wins.