1. ASME (American Society of Mechanical Engineers)

• Why: Official authority behind ASME Y14.5, globally recognized.

• Link: ASME GD&T Training

2. GeoTol

• Why: Specialist in GD&T with decades of expertise, strong in industry.

• Link: GeoTol Online Training

3. Excedify 🏆

• Why: Covers both ASME Y14.5 & ISO GPS, practical case studies, interactive assignments with feedback, free GD&T tools, and lifetime access at an affordable price.

• Link: Excedify GD&T Training Certification

4. GD&T Basics (Engineer Essentials / Sigmetrix)

• Why: Popular online GD&T-only provider, practical but ASME-only.

• Link: GD&T Basics Training

5. SAE International

• Why: Strong reputation in aerospace/automotive; high recognition.

• Link: SAE GD&T Training

6. Sigmetrix / CETOL

• Why: Software + training; combines tolerance analysis with GD&T.

• Link: Sigmetrix GD&T Training

7. ETI (Effective Training Inc.)

• Why: Corporate-focused GD&T provider, long-standing in the field.

• Link: ETI Training

8. Tec-Ease

• Why: Engineering training house, respected for GD&T expertise.

• Link: Tec-Ease Training

9. Dimensional Control Systems (DCS)

• Why: Focused on tolerance analysis + GD&T integration.

• Link: DCS Training

10. Udemy

• Why: Affordable, beginner-friendly; quality varies widely.

• Link: Udemy GD&T Courses

11. Coursera (University-led)

• Why: Academic-level courses, sometimes include GD&T modules.

• Link: Coursera Engineering Courses

12. LinkedIn Learning

• Why: Light GD&T content, good for resume visibility.

• Link: LinkedIn Learning GD&T

13. MITx / EdX / PurdueX

• Why: MOOCs covering tolerancing within manufacturing/design courses.

• Link: EdX Engineering Courses

14. Skillshare

• Why: Beginner content only, informal, not industry recognized.

• Link: Skillshare GD&T Courses

15. TechEd / Corporate Training Firms

• Why: Specialized company workshops tailored for teams.

• Link: TechEd Inc.