Geometric dimensioning and tolerancing (GD&T) is a symbolic language that’s used on engineering drawings to convey design intent to manufacturers. While it doesn’t play as prominent a role in the earliest stages of hardware product development, GD&T becomes far more critical once you transition from the prototype to the production stage.
Many engineers, if not most, don’t receive formal training in GD&T. Most universities don’t offer it as a course, and if they do, it’s in a very limited capacity (i.e., a chapter in a book or a 6-hour/one-day class). These offerings are totally insufficient to gain both a proper understanding of and the ability to use GD&T.
When an engineer encounters a situation or reaches a level in their career when they need to use GD&T, they typically take the self-taught approach or try to find an experienced mentor or a qualified program that can teach them.
Whichever learning method you prefer, here are several resources (paid and free) that you can use to improve your GD&T proficiency.
ASME Y14.5-2018 Dimensioning and Tolerancing Standard
This is the single source of truth for all things related to GD&T, and a natural starting point if you want to either begin or progress your GD&T journey.
The American Society of Engineers’ (ASME) Y14.5 standard is an industry-recognized, authoritative guideline for GD&T. The 2018 version replaced the 2019 one and was reviewed/reaffirmed in 2024, so it remains in effect (at least as of the time this was written).
The standard includes the geometric symbols, rules, definitions, defaults, requirements, and best practices for using and interpreting GD&T.
You can purchase a print or digital copy of the ASME Y14.5-2018 standard, which runs around $250.
In addition to the standard itself, ASME also offers a number of learning resources, including:
- In-person and virtual courses
- Guided study
- Self-study
- Corporate training
Obviously all of these resources can be purchased by individuals, but see if your company will purchase one for your engineering team since it will improve the work they’re doing and is a valuable skill for all mechanical and design engineers to have.
GD&T Basics
GD&T Basics provides a robust learning platform with highly organized, detailed learning content for mastering geometric dimensioning and tolerancing.
GD&T Basics offers individual and group training, and a variety of learning formats, including:
- Self-paced courses for individuals
- Self-paced training for teams
- Onsite GD&T training
- Public training
- Custom team virtual training
- Customized consulting
They offer four formal courses that extensively cover not only GD&T but print reading and inspection.
Print Reading & Tolerances
Key topics
- Engineering drawings
- Anatomy of a drawing
- Bill of materials (BOM)
- Types of drawing views
- Types of lines
- Drawing symbols and callouts
- Special requirement callouts
- Types of tolerances
- GD&T basics
Time to complete: 8-12 hours
GD&T Fundamentals
Key topics
- Main requirements and terminology of the ASME Y14.5-2018 standard
- Symbols and application
- Feature control frames (FCFs)
- Max material condition
- Datums
Time to complete: 10-14 hours
Advanced GD&T
Key topics
- Datums
- Datum modifiers and functional gaging
- Composite tolerances
- Hole and fastener guide
- Envelope and boundary tolerance formulas
- General advanced symbols and concepts
Time to complete: 15-24 hours
Inspections
Key topics
- Measurement considerations
- Metrology equipment
- Hand tools for local sizes
- CMM inspections for sizes and envelopes
- Datum simulation and DFRs
- Feature inspection framework
- Types of controls
- Material modifiers
Individuals and teams who purchase a program (or bundle) have access to instructor email support, bonus content, charts, drawing examples, practice worksheets, printable handouts, quizzes, knowledge checks, and a certificate of completion.
On top of their coursework, GD&T Basics also offers a library of free resources.
Dean Odell
If a GD&T celebrity were to exist, Dean Odell would be your guy (and he also happens to be an instructor for GD&T Basics). He is most famous for his YouTube channel, which has nearly 34,000 subscribers and over 200 videos!
His YouTube videos cover print reading, GD&T basics, tolerance stackup, GD&T inspection, and manufacturing processes.
Dean’s YouTube videos are highly detailed, get into the nitty gritty details of GD&T, and are totally free. He also offers custom, in-person group trainings that run between 12 and 16 hours, which you can sign up for on his website.
Amanda White
Tre Tiff
