---
type: "gdt-symbol"
name: "Tangent Plane"
symbol: "Ⓣ"
unicode: "U+24C9"
unicode_name: "CIRCLED LATIN CAPITAL LETTER T"
category: "modifier"
category_name: "Modifiers and material conditions"
datum_required: "never"
aliases: ["tangent plane gdt"]
standard: "ASME Y14.5 (cited, not reproduced); ISO 1101"
verified: "August 1, 2026"
url: https://shopmath.org/gdt/tangent-plane
---

# Tangent Plane (Ⓣ) — GD&T Modifier Symbol and Meaning

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.

- **Symbol**: Ⓣ (Unicode U+24C9)
- **Category**: Modifiers and material conditions
- **Datum reference**: never references a datum
- **Standard**: ASME Y14.5 (cited, not reproduced); ISO 1101

## Tangent Plane at a Glance

| Property | Value |
| --- | --- |
| Characteristic | Tangent Plane |
| Symbol | Ⓣ |
| Unicode codepoint | U+24C9 |
| Unicode name | CIRCLED LATIN CAPITAL LETTER T |
| Category | Modifiers and material conditions |
| Datum reference | never references a datum |
| Standard | ASME Y14.5 (cited, not reproduced); ISO 1101 |

## How Tangent Plane Behaves

Tangent Plane belongs to the modifiers and material conditions group. Change how a geometric tolerance is interpreted or verified.

## Other Modifiers and material conditions Controls

The controls in the same category — the ones a drawing is choosing between when it specifies tangent plane.

| Control | Symbol | Tolerance zone or effect | Datum |
| --- | --- | --- | --- |
| [Maximum Material Condition (MMC)](https://shopmath.org/gdt/maximum-material-condition.md) | Ⓜ | States that the stated tolerance applies when the feature contains the most material — the largest pin or the smallest hole. | never references a datum |
| [Least Material Condition (LMC)](https://shopmath.org/gdt/least-material-condition.md) | Ⓛ | The mirror of MMC: the stated tolerance applies when the feature contains the least material — the smallest pin or the largest hole. | never references a datum |
| [Regardless of Feature Size (RFS)](https://shopmath.org/gdt/regardless-of-feature-size.md) | Ⓢ | The default condition since 1994: the geometric tolerance applies at whatever size the feature is actually produced, with no bonus. | never references a datum |
| [Projected Tolerance Zone](https://shopmath.org/gdt/projected-tolerance-zone.md) | Ⓟ | Zone projected above the feature | never references a datum |
| [Free State](https://shopmath.org/gdt/free-state.md) | Ⓕ | Says the requirement is to be verified with no restraining force applied. | never references a datum |
| [Unequally Disposed Profile](https://shopmath.org/gdt/unequally-disposed-profile.md) | Ⓤ | Profile band split unevenly about the true profile | never references a datum |
| [Diameter](https://shopmath.org/gdt/diameter.md) | ⌀ | Inside a feature control frame this makes the tolerance zone cylindrical rather than a pair of parallel planes. | never references a datum |

## Sources and Method for Tangent Plane

### Tangent Plane definition

- **Source**: 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.
- **Method**: compiled
- **Verified against**: Unicode Character Database codepoint check; 98/98 structural checks passed

### Assumptions

- Descriptions are original prose. No ASME Y14.5 definitional text, worked example or figure is reproduced — the standard is cited, not copied.
- Symbol glyphs and codepoints are from the Unicode Character Database; a drawing may render the same characteristic with a different font.
- 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

## 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 GD&T symbol for tangent plane?

Tangent Plane uses the Ⓣ symbol — Unicode U+24C9 (CIRCLED LATIN CAPITAL LETTER T). It sits in the first compartment of the feature control frame.

### Does Tangent Plane need a datum?

Tangent Plane never references a datum. It qualifies how another control is interpreted rather than establishing a tolerance zone of its own.

## Related pages

- Previous control: [Free State](https://shopmath.org/gdt/free-state.md) (Ⓕ)
- Next control: [Unequally Disposed Profile](https://shopmath.org/gdt/unequally-disposed-profile.md) (Ⓤ)
- All symbols: [GD&T symbol reference](https://shopmath.org/gdt.md)
- Tolerances: [ISO 286 fit reference](https://shopmath.org/fits.md)

---

*Source: [ShopMath](https://shopmath.org/gdt/tangent-plane) — data verified August 1, 2026. Reference data; verify against the governing standard before manufacture.*