What centrifugal force is
Centrifugal force is the outward-feeling force experienced by an object moving in a circular path, as observed from within the rotating frame of reference. It has the same magnitude as the real, inward-pointing centripetal force that keeps the object moving in a circle.
The formula used
This calculator uses F = mv²/r, where m is mass, v is the object’s tangential speed, and r is the radius of the circular path. This is the same formula used for centripetal force, since the two are equal in magnitude and opposite in the frame from which they’re described.
Centrifugal force is technically a fictitious (inertial) force that only appears in a rotating reference frame; in an inertial (non-rotating) frame, the real force at play is centripetal force directed toward the center. For general physics education purposes.