standard
ASME Y14.5-2018 Dimensioning & Tolerancing Best Practices
A practitioner's guide to the standard that defines how engineering intent is communicated on drawings and digital models ā covering fundamental rules, datum reference frames, all geometric characteristics, material condition modifiers, and actionable best practices. š ASME Y14.5-2018 š§ GD&T / Engineering Drawing š Based on 2018 revision
Published May 30, 2026 - Maintained by Ashish Kapoor
This technical page is maintained by Ashish Kapoor, a project engineering lead. Use it as a learning and calculation-review aid, then verify critical work against current standards, project documents, supplier data, and competent engineering review.
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Table of Contents
ASME Y14.5-2018 is the authoritative American National Standard for dimensioning and tolerancing in engineering drawings and digital product definitions. It establishes the symbols, rules, definitions, requirements, defaults, and recommended practices that engineers use to communicate geometric requirements ā size, form, orientation, location, and profile ā from design through manufacturing and inspection.
The 2018 revision (which supersedes ASME Y14.5-2009) made several key changes: the concentricity and symmetry symbols were eliminated (other characteristics now provide more direct and unambiguous control), profile tolerancing for location is emphasized over plus/minus tolerancing, and model-based definition (MBD) support was expanded throughout.