What is the Tangent Plane symbol in GD&T?

Ⓣ — Unicode U+24C9 (CIRCLED LATIN CAPITAL LETTER T). It goes in the first compartment of the feature control frame, ahead of the tolerance value.

Does Tangent Plane need a datum?

Never references a datum. The tolerance zone floats to best-fit the feature, so this control says nothing about where the feature sits relative to anything else.

Which GD&T modifiers are in the same group as Tangent Plane?

Tangent Plane is one of 8 modifier modifiers: Tangent Plane, Maximum Material Condition (MMC), Least Material Condition (LMC), Regardless of Feature Size (RFS), Projected Tolerance Zone, Free State, Unequally Disposed Profile, Diameter.

GD&T · Modifier · ASME Y14.5

Tangent Plane GD&T Symbol — Meaning and Datum Rule

https://shopmath.org/gdt/tangent-plane · data verified August 1, 2026

Tangent Plane (Ⓣ) is a GD&T modifier: it changes how a tolerance is interpreted rather than defining a zone of its own. It never references a datum.

Symbol: Ⓣ
Unicode: U+24C9
Category: Modifier
Datum: never

Tangent Plane · GD&T modifier symbol

Ⓣ

Unicode: U+24C9
Datum: never

Tangent Plane qualifies another tolerance rather than standing on its own — it appears after the tolerance value or the datum reference it modifies.

What Tangent Plane Controls in GD&T

Evaluates an orientation control against a plane resting on the high points of the surface rather than against every point of it. Surface waviness inside the contact envelope is then ignored, which is appropriate when the surface's job is to seat against another face.

The Tangent Plane 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.

Tangent Plane — GD&T symbol, tolerance zone and datum rule
Property	Value
Symbol	Ⓣ
Unicode codepoint	U+24C9 (CIRCLED LATIN CAPITAL LETTER T)
Category	Modifiers and material conditions — Change how a geometric tolerance is interpreted or verified.
Tolerance zone	n/a — modifier
Datum reference	Never references a datum. The tolerance zone floats to best-fit the feature, so this control says nothing about where the feature sits relative to anything else.
Standard	ASME Y14.5 (cited, not reproduced); ISO 1101

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 Modifiers Related to Tangent Plane

Tangent Plane is a modifier modifier . Change how a geometric tolerance is interpreted or verified. These are the others in that group — the ones a drawing usually chooses between.

GD&T modifier symbols related to Tangent Plane
Symbol	Datum	Tolerance zone
Maximum Material Condition (MMC)	never	n/a — modifier
Least Material Condition (LMC)	never	n/a — modifier
Regardless of Feature Size (RFS)	never	n/a — modifier
Projected Tolerance Zone	never	Zone projected above the feature
Free State	never	n/a — modifier
Unequally Disposed Profile	never	Profile band split unevenly about the true profile
Diameter	never	n/a — modifier

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

Sources and Method for the Tangent Plane GD&T Reference

Tangent Plane 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 Tangent Plane GD&T Reference

Citation

ShopMath. "Tangent Plane GD&T Symbol — Meaning and Datum Rule." ShopMath, verified August 1, 2026, https://shopmath.org/gdt/tangent-plane

BibTeX

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

Permanent URL

https://shopmath.org/gdt/tangent-plane

Common Questions About Tangent Plane in GD&T

What does Tangent Plane mean in GD&T?: Evaluates an orientation control against a plane resting on the high points of the surface rather than against every point of it. Surface waviness inside the contact envelope is then ignored, which is appropriate when the surface's job is to seat against another face.
What is the Tangent Plane symbol in GD&T?: Ⓣ — Unicode U+24C9 (CIRCLED LATIN CAPITAL LETTER T). It goes in the first compartment of the feature control frame, ahead of the tolerance value.
Does Tangent Plane need a datum?: Never references a datum. The tolerance zone floats to best-fit the feature, so this control says nothing about where the feature sits relative to anything else.
Which GD&T modifiers are in the same group as Tangent Plane?: Tangent Plane is one of 8 modifier modifiers: Tangent Plane, Maximum Material Condition (MMC), Least Material Condition (LMC), Regardless of Feature Size (RFS), Projected Tolerance Zone, Free State, Unequally Disposed Profile, Diameter.

Every GD&T symbol and modifier