What is the difference between circular runout and total runout?

Circular runout controls the variation of a surface during one full rotation at any single cross-section perpendicular to the datum axis. Total runout controls the entire surface simultaneously during rotation, including variations along the length. Circular runout is measured at individual cross-sections, while total runout requires checking all points on the surface. Total runout is more restrictive and controls both circularity and cylindricity/straightness of the surface.