What is the Concentricity symbol in GD&T?

◎ — Unicode U+25CE. It goes in the first compartment of the feature control frame, ahead of the tolerance value.

Does Concentricity need a datum?

Always references at least one datum. Without a datum reference frame the callout is incomplete and the drawing is ambiguous.

What shape is the Concentricity tolerance zone?

A cylinder centred on the datum axis, applied to derived median points. Every point of the controlled feature has to lie inside that zone for the part to pass.

Which GD&T controls are in the same group as Concentricity?

Concentricity is one of 3 location controls: Concentricity, Position, Symmetry.

GD&T · Location · ASME Y14.5

Concentricity GD&T Symbol — Meaning and Datum Rule

https://shopmath.org/gdt/concentricity · data verified August 1, 2026

Concentricity (◎) is a GD&T location control, and its tolerance zone is a cylinder centred on the datum axis, applied to derived median points. It always references a datum.

Symbol: ◎
Unicode: U+25CE
Category: Location
Datum: always

Concentricity · GD&T location symbol

◎

Unicode: U+25CE
Datum: always
Zone: A cylinder centred on the datum axis, applied to derived median points

The value in the feature control frame is the width or diameter of that zone, in the drawing's units.

What Concentricity Controls in GD&T

Constrains the derived median points of a feature to a cylindrical zone about a datum axis. It is expensive to inspect because it requires deriving opposed-point midpoints rather than probing a surface, so runout or position is usually the better choice; ASME Y14.5-2018 removed it from the standard for exactly that reason.

The Concentricity GD&T Symbol, Zone and Datum Rule

The symbol as it appears in the feature control frame, with the codepoint to type it and the rule it carries.

Concentricity — GD&T symbol, tolerance zone and datum rule
Property	Value
Symbol	◎
Unicode codepoint	U+25CE
Category	Location controls — Control where a feature sits relative to a datum reference frame.
Tolerance zone	A cylinder centred on the datum axis, applied to derived median points
Datum reference	Always references at least one datum. Without a datum reference frame the callout is incomplete and the drawing is ambiguous.
Standard	ASME Y14.5 (cited, not reproduced); ISO 1101
Also called	concentricity vs runout

The symbol character is the Unicode codepoint used in drawings and CAD annotations; drafting standards render it with defined proportions that the font approximates.

GD&T Controls Related to Concentricity

Concentricity is a location control. Control where a feature sits relative to a datum reference frame. These are the others in that group — the ones a drawing usually chooses between.

GD&T location symbols related to Concentricity
Symbol	Datum	Tolerance zone
Position	always	A cylinder (or two parallel planes) centred on the true position
Symmetry	always	Two parallel planes centred on the datum centre plane

Ordered as they appear in the feature control frame reference, form through runout, then modifiers.

Sources and Method for the Concentricity GD&T Reference

Concentricity symbol and rulescompiled

Symbols and codepoints: Unicode Character Database (Unicode License v3). Characteristic list cross-checked against NASA MSFC GD&T Basics (public domain). Descriptions written from scratch; no ASME Y14.5 text reproduced.

Verified against Unicode Character Database codepoint check; 98/98 structural checks passed

Compiled from independent public sources that agree cell-for-cell.

Assumptions

The standard is cited, never reproduced: no ASME Y14.5 definitional text, worked example or figure appears on this site. The description above is original prose.
ASME Y14.5 and ISO 1101 differ in places — the ISO system uses the envelope requirement differently and does not carry every ASME modifier. Where a drawing names a standard, that standard governs.
Dataset scope: EXCLUDED: all ASME Y14.5 definitional text, worked examples and figures. Every description on this site is original prose.

Data last verified

August 1, 2026

How this data is built and checked →

How to Cite This Concentricity GD&T Reference

Citation

ShopMath. "Concentricity GD&T Symbol — Meaning and Datum Rule." ShopMath, verified August 1, 2026, https://shopmath.org/gdt/concentricity

BibTeX

@misc{shopmath-gdt-concentricity,
  title        = {Concentricity GD&T Symbol — Meaning and Datum Rule},
  author       = {{ShopMath}},
  year         = {2026},
  howpublished = {\url{https://shopmath.org/gdt/concentricity}},
  note         = {Data verified 2026-08-01}
}

Permanent URL

https://shopmath.org/gdt/concentricity

Common Questions About Concentricity in GD&T

What does Concentricity mean in GD&T?: Constrains the derived median points of a feature to a cylindrical zone about a datum axis. It is expensive to inspect because it requires deriving opposed-point midpoints rather than probing a surface, so runout or position is usually the better choice; ASME Y14.5-2018 removed it from the standard for exactly that reason.
What is the Concentricity symbol in GD&T?: ◎ — Unicode U+25CE. It goes in the first compartment of the feature control frame, ahead of the tolerance value.
Does Concentricity need a datum?: Always references at least one datum. Without a datum reference frame the callout is incomplete and the drawing is ambiguous.
What shape is the Concentricity tolerance zone?: A cylinder centred on the datum axis, applied to derived median points. Every point of the controlled feature has to lie inside that zone for the part to pass.
Which GD&T controls are in the same group as Concentricity?: Concentricity is one of 3 location controls: Concentricity, Position, Symmetry.

Every GD&T symbol and modifier