GD&T · Orientation · ASME Y14.5
Parallelism GD&T Symbol — Meaning and Datum Rule
https://shopmath.org/gdt/parallelism · data verified August 1, 2026
Parallelism (∥) is a GD&T orientation control, and its tolerance zone is two parallel planes (or a cylinder, for an axis) parallel to the datum. It always references a datum.
- Symbol
- ∥
- Unicode
- U+2225
- Category
- Orientation
- Datum
- always
Parallelism · GD&T orientation symbol
∥
- Unicode
- U+2225
- Datum
- always
- Zone
- Two parallel planes (or a cylinder, for an axis) parallel to the datum
The value in the feature control frame is the width or diameter of that zone, in the drawing's units.
What Parallelism Controls in GD&T
Angularity's zero-degree special case. It limits how much a surface or axis may tilt relative to a datum, but places no limit on how far away it sits — distance is the job of the linear dimension or of a profile or position callout.
The Parallelism 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+2225 (PARALLEL TO) |
| Category | Orientation controls — Control the angle of a feature relative to a datum, but not its distance. |
| Tolerance zone | Two parallel planes (or a cylinder, for an axis) parallel to the datum |
| 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 | flatness vs parallelism |
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 Parallelism GD&T Reference
- Parallelism 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 Parallelism GD&T Reference
Citation
ShopMath. "Parallelism GD&T Symbol — Meaning and Datum Rule." ShopMath, verified August 1, 2026, https://shopmath.org/gdt/parallelism
BibTeX
@misc{shopmath-gdt-parallelism,
title = {Parallelism GD&T Symbol — Meaning and Datum Rule},
author = {{ShopMath}},
year = {2026},
howpublished = {\url{https://shopmath.org/gdt/parallelism}},
note = {Data verified 2026-08-01}
}Permanent URL
https://shopmath.org/gdt/parallelism
Common Questions About Parallelism in GD&T
What does Parallelism mean in GD&T?
- Angularity's zero-degree special case. It limits how much a surface or axis may tilt relative to a datum, but places no limit on how far away it sits — distance is the job of the linear dimension or of a profile or position callout.
What is the Parallelism symbol in GD&T?
- ∥ — Unicode U+2225 (PARALLEL TO). It goes in the first compartment of the feature control frame, ahead of the tolerance value.
Does Parallelism 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 Parallelism tolerance zone?
- Two parallel planes (or a cylinder, for an axis) parallel to the datum. 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 Parallelism?
- Parallelism is one of 3 orientation controls: Parallelism, Angularity, Perpendicularity.