GD&T Symbols Chart: Free Printable Reference Sheet for Your Shop Floor

One Page. Every Symbol You Need.

When you are reading an engineering drawing and you need to quickly confirm what a GD&T (Geometric Dimensioning and Tolerancing) symbol means, you don’t want to search through a textbook. You want a fast, accurate reference.

This chart covers all 14 geometric tolerance symbols defined in the ASME Y14.5 standard, organized by their five categories. It also includes the feature control frame layout and the most common modifiers. Consider this your quick-look reference for GD&T.

Complete GD&T Symbols Chart

Category	Symbol	Name	Tolerance Zone	Datum?	Controls
Form	⏥	Flatness	Two parallel planes	No	How flat a surface is
Form	⏤	Straightness	Two parallel lines or cylinder	No	How straight a line or axis is
Form	○	Circularity	Two concentric circles	No	How round a cross-section is
Form	⌭	Cylindricity	Two coaxial cylinders	No	Roundness + straightness of a cylinder
Orientation	⟂	Perpendicularity	Two parallel planes or cylinder	Yes	90° relationship to datum
Orientation	∥	Parallelism	Two parallel planes or cylinder	Yes	Parallel relationship to datum
Orientation	∠	Angularity	Two parallel planes or cylinder	Yes	Specified angle to datum
Location	⊕	True Position	Cylinder or two parallel planes	Yes	Feature location from true (basic) position
Location	◎	Concentricity	Cylinder	Yes	Median points relative to datum axis
Location	⌯	Symmetry	Two parallel planes	Yes	Median points relative to datum center plane
Profile	⌒	Profile of a Line	Two offset curves	Optional	2D cross-sectional shape
Profile	⌓	Profile of a Surface	Two offset surfaces	Optional	3D surface shape
Runout	↗	Circular Runout	FIM at each cross-section	Yes	Surface variation per cross-section during rotation
Runout	↗↗	Total Runout	FIM across entire surface	Yes	Surface variation across full feature during rotation

Feature Control Frame Anatomy

Every GD&T callout on a drawing appears inside a feature control frame. Understanding its layout is the key to reading any tolerance.

Example reading: [⊕ | ⌀0.50 Ⓜ | A | B | C] reads as: “True position, 0.50 mm diameter cylindrical tolerance zone at Maximum Material Condition, referenced to datums A, B, and C.”

Common GD&T Modifiers

Symbol	Name	Meaning
Ⓜ	Maximum Material Condition (MMC)	Tolerance applies at MMC size; bonus tolerance available
Ⓛ	Least Material Condition (LMC)	Tolerance applies at LMC size; bonus tolerance available
⌀	Diameter	Tolerance zone is cylindrical
Ⓕ	Free State	Tolerance applies in the unrestrained condition
Ⓣ	Tangent Plane	Tolerance applies to a plane contacting the high points
Ⓟ	Projected Tolerance Zone	Tolerance zone extends beyond the feature

Understanding the Five Categories

The 14 symbols are organized into five categories based on what aspect of geometry they control. Knowing the category tells you a lot about how the tolerance works before you even look at the details.

Form (4 symbols)

Controls the shape of individual features. No datum required. These are the simplest GD&T controls.

• Flatness: Surface must lie between two parallel planes.
• Straightness: Line element or axis must lie within a defined zone.
• Circularity: Each cross-section must lie between two concentric circles.
• Cylindricity: Entire surface must lie between two coaxial cylinders.

Orientation (3 symbols)

Controls angular relationships between features and datums. Always requires at least one datum.

• Perpendicularity: Feature must be within tolerance of 90° to the datum.
• Parallelism: Feature must be within tolerance of 0° (parallel) to the datum.
• Angularity: Feature must be within tolerance of a specified angle to the datum.

Location (3 symbols)

Controls where a feature sits relative to datums. Always requires datum references.

• True Position: Feature center must be within tolerance of its theoretically exact location.
• Concentricity: Median points must be within tolerance of datum axis. Rarely used.
• Symmetry: Median points must be within tolerance of datum center plane. Rarely used.

Profile (2 symbols)

Controls surface shape relative to the true profile. Datums are optional.

• Profile of a Line: Each cross-sectional element must match the true profile within tolerance.
• Profile of a Surface: The entire surface must match the true profile within tolerance.

Runout (2 symbols)

Controls surface variation during rotation. Always requires a datum axis.

• Circular Runout: FIM (Full Indicator Movement) at each individual cross-section during rotation.
• Total Runout: FIM across the entire surface during rotation.

Datum Feature Symbol Reference

Datums are identified on drawings by a datum feature symbol: a letter inside a rectangular frame, attached to the feature by a leader line or placed on the dimension line or feature control frame extension.

Key rules for datums:

• Datum letters are assigned alphabetically (A, B, C…), skipping I, O, and Q to avoid confusion with numbers.
• The primary datum constrains the most degrees of freedom.
• Datum order in the feature control frame matters. A|B|C is different from B|A|C.
• A datum is a theoretical reference. The physical feature is called the datum feature. The physical surface or device used during inspection is the datum feature simulator.

Tips for Using This Chart

Print it out. Pin a copy next to your workstation, CMM (Coordinate Measuring Machine), or in the quality lab. Having the reference visible saves time when reviewing drawings.

Bookmark this page. For digital reference, keep this chart accessible in your browser for quick lookups during design reviews, PPAP submissions, or inspection planning.

Use it as a study tool. If you are learning GD&T, cover the “Controls” column and test yourself on what each symbol does. Then cover the “Symbol” column and test yourself on recognizing the name and category.

Share it with your team. When everyone on the shop floor speaks the same GD&T language, communication errors drop and inspection consistency improves.

Frequently Asked Questions