What is True Position?

In Geometric Dimensioning and Tolerancing (GD&T), the True Position symbol Ⓣ defines the exact, theoretically perfect location of a feature relative to a specified datum reference frame. It is most commonly applied to holes, slots, and other features that require precise alignment and spacing.

True Position tolerance ensures that the feature’s axis, center, or surface lies within a defined cylindrical or rectangular tolerance zone, rather than just relying on linear ± dimensions. This improves both design intent communication and manufacturing consistency.

How True Position is Used

• Hole and fastener alignment – Ensures bolt holes line up correctly with mating parts, even when multiple datums are referenced.
• Assembly accuracy – Controls variation in the location of features, preventing misalignment during product assembly.
• Tolerance optimization – Allows looser manufacturing tolerances while still meeting functional requirements, reducing cost without sacrificing quality.
• Datum reference system – True Position is always applied in relation to one or more datums (primary, secondary, tertiary) to establish exact feature placement.

Example of True Position

Imagine a hole pattern on a flange. Instead of dimensioning each hole with ± tolerances in X and Y, True Position defines a cylindrical tolerance zone around the true (theoretical) center of the hole. As long as the actual hole axis lies within this zone, the part is acceptable.

Why True Position Matters

True Position is one of the most powerful GD&T symbols because it defines both location and orientation in a single control. It ensures that mating parts fit and function correctly, especially in complex assemblies.

By using True Position, engineers can better communicate design intent, reduce ambiguity, and ensure components are manufactured and inspected to meet functional requirements.