GD&T · Form · ASME Y14.5
Flatness GD&T Symbol — Meaning and Datum Rule
https://shopmath.org/gdt/flatness · data verified August 1, 2026
Flatness (⏥) is a GD&T form control, and its tolerance zone is two parallel planes. It never references a datum.
- Symbol
- ⏥
- Unicode
- U+23E5
- Category
- Form
- Datum
- never
Flatness · GD&T form symbol
⏥
- Unicode
- U+23E5
- Datum
- never
- Zone
- Two parallel planes
The value in the feature control frame is the width or diameter of that zone, in the drawing's units.
What Flatness Controls in GD&T
Requires every point of a surface to fall between two parallel planes separated by the tolerance value. Because the zone floats to best-fit the surface, flatness says nothing about where the surface sits relative to anything else — that is what parallelism and profile are for.
The Flatness 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.
| Property | Value |
|---|---|
| Symbol | ⏥ |
| Unicode codepoint | U+23E5 (FLATNESS) |
| Category | Form controls — Control the shape of a single feature against itself. Never reference a datum. |
| Tolerance zone | Two parallel planes |
| 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 |
| Also called | flatness symbol, flatness tolerance |
The symbol character is the Unicode codepoint used in drawings and CAD annotations; drafting standards render it with defined proportions that the font approximates.
Sources and Method for the Flatness GD&T Reference
- Flatness 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 to Cite This Flatness GD&T Reference
Citation
ShopMath. "Flatness GD&T Symbol — Meaning and Datum Rule." ShopMath, verified August 1, 2026, https://shopmath.org/gdt/flatness
BibTeX
@misc{shopmath-gdt-flatness,
title = {Flatness GD&T Symbol — Meaning and Datum Rule},
author = {{ShopMath}},
year = {2026},
howpublished = {\url{https://shopmath.org/gdt/flatness}},
note = {Data verified 2026-08-01}
}Permanent URL
https://shopmath.org/gdt/flatness
Common Questions About Flatness in GD&T
What does Flatness mean in GD&T?
- Requires every point of a surface to fall between two parallel planes separated by the tolerance value. Because the zone floats to best-fit the surface, flatness says nothing about where the surface sits relative to anything else — that is what parallelism and profile are for.
What is the Flatness symbol in GD&T?
- ⏥ — Unicode U+23E5 (FLATNESS). It goes in the first compartment of the feature control frame, ahead of the tolerance value.
Does Flatness 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.
What shape is the Flatness tolerance zone?
- Two parallel planes. 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 Flatness?
- Flatness is one of 4 form controls: Flatness, Straightness, Circularity, Cylindricity.