Basic dimension

In technical drawing, a basic dimension is a theoretically exact dimension, given from a datum to a feature of interest. In Geometric dimensioning and tolerancing, basic dimensions are defined as a numerical value used to describe the theoretically exact size, profile, orientation or location of a feature or datum target. For basic dimensions, the tolerance is most commonly indicated on a general note, or located in a supplementary block of the drawing format. To facilitate manufactureability, a feature control frame is often used to assign a dimensional tolerance to the feature that is referenced in by the basic dimension. Chained basic dimensions do not create tolerance stack up. Proper tolerance must be inferred by Datums referenced in the feature control frame, and not by dimension arrows or start points.