Definition
Total runout is a geometric tolerance that controls the combined form and position variation of a surface as a part rotates fully around a datum axis.
What it means for the calculation
Tight total runout usually requires the part to be finished (often ground) while mounted on the same axis used for inspection, since any variation in form, position or balance shows up in the same measurement.
Where it appears on the drawing
In a feature control frame with the ⌰ symbol, a tolerance value, and a datum axis reference.
Common mistakes
Confusing total runout (measured over a whole surface while rotating) with circular runout (measured at a single cross-section); assuming total runout only checks roundness, when it also captures straightness, coaxiality and perpendicularity errors together.
Tight total runout usually requires the part to be finished (often ground) while mounted on the same axis used for inspection, since any variation in form, position or balance shows up in the same measurement.
See how Blake reviews a partFrequently asked questions
What is the difference between total runout and circular runout?
Circular runout checks a single cross-section while rotating; total runout checks the entire surface while rotating.
Does total runout need a datum axis?
Yes, it is always measured relative to a specified axis of rotation.
Why is total runout considered a strict tolerance?
Because it combines several possible errors (roundness, straightness, coaxiality) into one check, so it catches problems that individual tolerances might miss.