All 14 geometric characteristic symbols organized by category: form, orientation, location, runout, and profile. Each entry includes the Unicode symbol, definition, typical tolerance range, and whether a datum reference is required.
Last updated April 2026
| Symbol | Name | Category | Definition | Typical Range | Datum |
|---|---|---|---|---|---|
| ⏥ | Flatness | Form | All points on a surface must lie between two parallel planes separated by the tolerance value. | 0.001" - 0.010" | No |
| ⏤ | Straightness | Form | All points along a line element or axis must lie within a tolerance zone (two parallel lines or a cylinder). | 0.001" - 0.010" | No |
| ○ | Circularity | Form | All points on any cross-section perpendicular to the axis must lie between two concentric circles. | 0.001" - 0.005" | No |
| ⌭ | Cylindricity | Form | All points on the surface must lie between two coaxial cylinders separated by the tolerance value. | 0.001" - 0.010" | No |
| ⊥ | Perpendicularity | Orientation | A surface, axis, or plane must be within a tolerance zone perpendicular to a datum reference. | 0.001" - 0.010" | Yes |
| ∠ | Angularity | Orientation | A surface, axis, or plane must be within a tolerance zone at the specified angle to a datum reference. | 0.001" - 0.010" | Yes |
| ∥ | Parallelism | Orientation | A surface, axis, or plane must be within a tolerance zone parallel to a datum reference. | 0.001" - 0.010" | Yes |
| ⌖ | Position | Location | The axis or center plane of a feature must fall within a cylindrical or parallel-plane tolerance zone at true position. | 0.005" - 0.030" | Yes |
| ◎ | Concentricity | Location | All median points of a feature must lie within a cylindrical tolerance zone coaxial with a datum axis. | 0.001" - 0.010" | Yes |
| ⌯ | Symmetry | Location | The median points of a feature must lie within a tolerance zone equally disposed about a datum center plane. | 0.005" - 0.020" | Yes |
| ↗ | Circular Runout | Runout | The surface at any single cross-section must not vary more than the tolerance during one full rotation about a datum axis. | 0.001" - 0.005" | Yes |
| ↗↗ | Total Runout | Runout | The entire surface must not vary more than the tolerance during full rotation and translation along a datum axis. | 0.001" - 0.010" | Yes |
| ⌒ | Profile of a Line | Profile | Each line element of a surface must lie within a two-dimensional tolerance zone defined by the true profile. | 0.005" - 0.020" | No |
| ⌓ | Profile of a Surface | Profile | The entire surface must lie within a three-dimensional tolerance zone defined by the true profile. | 0.005" - 0.030" | No |
GD&T (Geometric Dimensioning and Tolerancing) is a symbolic language defined by ASME Y14.5 for specifying allowable variation in part geometry beyond simple plus/minus dimensions. It uses 14 characteristic symbols to control form, orientation, location, runout, and profile, enabling precise communication of design intent between engineering and manufacturing.
Orientation controls (parallelism, perpendicularity, angularity), location controls (position, concentricity, symmetry), and runout controls (circular runout, total runout) all require datum references. Form controls (flatness, straightness, circularity, cylindricity) do not require datums because they evaluate a feature independently against its own ideal shape.