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GD&T Symbols Reference Chart

This is your convenient guide for Geometric Dimensioning and Tolerancing (GD&T) symbols.  Click on any link below to lean more about each GD&T symbol or concept. You can also download a PDF version of this information by clicking the button:

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Control Type

 

Characteristic GD&T Symbol Notes
Form Flatness gd&t flatness symbol

Controls form (shape) of size and non-size features.

Datum reference is not allowed

Straightness
Circularity (Roundness) gd&t circularity symbol

Controls form (shape) of size features only.

Datum reference is not allowed

Cylindricity

Orientation

No relation between features

Perpendicularity gd&t perpendicularity symbol

Controls orientation (tilt) of surfaces, axes, or median planes for size and non-size features.

Datum reference required.

Optional: Angularity symbol may be used for all orientation controls.

Parallelism gd&t parallelism symbol
Angularity gd&t angularity symbol
Location
Position gd&t true position symbol Locates center points, axes and median planes for size features. Can also control orientation.  See also True Position.
Profile of a Surface

Locates surfaces by describing a tolerance zone around the surface or line.

Can also be used to control size, form, and orientation based on datum reference.

Profile of a Line gd&t profile of a line symbol
Runout Total Runout gd&t total runout symbol

Controls surface coaxiality

Can also control form and orientation of surfaces

Circular Runout gd&t circular runout symbol
Location of derived median points. Concentricity gd&t concentricity symbol

Locates derived median points of a feature

Not common, consider position, runout, or profile instead

Symmetry gd&t symmetry symbol

Feature Control Frames: Modifiers

Symbol
Modifier
Notes
Free State
Only applies if part is otherwise restrained.
Least Material Condition (LMC)
Useful to maintain minimum wall thickness
Provides bonus tolerance only for a feature of size
Projected Tolerance Zone
Useful on threaded holes for long studs
Regardless of Feature Size (RFS)
Not part of the 1994 standard
Tangent Plane
Useful for interfaces where form is not required
Unilateral
Appears in the 2009 version and refers to unequal profile distribution

Feature Control Frame describes the conditions and tolerances of a geometric control on a part’s feature.

Notes:

“RFS” means regardless of feature size.  It simply means that whatever GD&T callout you make, it is controlled independently of the size dimension of the part.  RFS is the default condition of all geometric tolerances (by rule #2 of GD&T) and requires no callout.

These GD&T symbols are provided as a reference for CNCCookbook’s free GD&T Tutorial. To learn what they mean, clicks the links, read on or check the Table of Contents for more information.

GD&T Tutorial Home          GD&T Symbols

 

Recently updated on February 19th, 2024 at 11:02 am