Centrifuge RCF Calculator

Convert between RPM and relative centrifugal force (×g), calculate k-factor and estimate sedimentation time.

Rotor speed (RPM)

Max rotor radius (cm)

Min rotor radius (cm)

Particle diameter (μm)

Tab to move between fields

RCF at rMax (×g)

1,006.2

RCF at rMin (×g)503.1

RCF ratio (max/min)2

k-factor19,485.1

RPM for 1,000 ×g2,991

Angular velocity (rad/s)314.16

Tip speed (m/s)31.42

Est. sedimentation time (min)15.2

Centripetal Accel Ms29,869.6

How to Use This Calculator

Enter the centrifuge rotor radius in millimeters (from rotor specs or measured to sample midpoint).
Input the desired RCF (relative centrifugal force) in xg from your protocol.
Review the calculated RPM to set on your centrifuge.
Alternatively, enter your RPM to back-calculate the RCF you are achieving.
Always verify rotor max speed and confirm RCF is within safe limits before running.

How the result changes with Rotor speed (RPM)

Rotor speed (RPM): Rotational speed in revolutions per minute.
Max rotor radius (cm): Distance from center of rotation to the bottom of the tube (rMax).
Min rotor radius (cm): Distance from center of rotation to the top of the liquid (rMin).
Particle diameter (μm): Diameter of particle to sediment, for time estimate (Stokes' law).

RCF at rMax (×g): Relative centrifugal force at maximum radius. RCF = 1.118×10⁻⁵ × r(cm) × RPM².
RCF at rMin (×g): Relative centrifugal force at minimum radius (top of liquid).
RCF ratio (max/min): Gradient of g-force across the tube. Closer to 1 is more uniform.
k-factor: Rotor clearing factor. Lower k = faster pelleting. k = 2.53×10¹¹ × ln(rMax/rMin) / RPM².
RPM for 1,000 ×g: RPM needed to achieve 1,000 ×g at the given max radius.
Angular velocity (rad/s): Angular velocity: ω = 2π × RPM / 60.
Tip speed (m/s): Linear speed at rotor tip. Most rotors are rated to ~100 m/s max.
Est. sedimentation time (min): Estimated time to pellet particles (Stokes' law, assuming Δρ=0.1 g/cm³ in water at 20 °C).

Identify Input Parameters
4 parameters
Rotor speed (RPM) = 3000, Max rotor radius (cm) = 10, Min rotor radius (cm) = 5, Particle diameter (μm) = 1 = 4 input(s) provided
Calculate RCF at rMax
RCF at rMax = 1.118e-5 * rotorRadiusCm * rpm * rpm
1006.2 = 1006.2
Calculate RCF at rMin
RCF at rMin = 1.118e-5 * rotorRadiusMinCm * rpm * rpm
503.1 = 503.1
Calculate RCF ratio
2 = 2