Becoming Certified in GD&T

I wrote about this a long time ago, but it’s worth mentioning again as the new year approaches (for people who still do New Year’s resolutions!).  Regular GD&T users should be aware of the certification process for GD&T Professionals.

The American Society of Mechanical Engineers (ASME) has established a credential for GD&T proficiency, called GDTP, which stands for ‘Geometric Dimensioning and Tolerancing Professional.’

It is a testing process that measures your ability to interpret and apply tolerances correctly. It is not a license to practice GD&T (no one can legislate that) but it is something that looks nice on your resume!

There are actually two certification levels: the Technologist Level, which measures your ability to read GD&T; and the Senior Level, which tests not only interpretation, but also the application of GD&T to a design. One does not necessarily need to become a Technologist first; some people go right for the Senior Level, although they are required to document at least five years of experience in GD&T (and they have a more difficult test!).

If you decide to pursue either level, be aware that the questions on the test come from all sections of the 1994 Y14.5 standard. (UPDATE — summer 2017: They now offer the exam based on the 2009 standard, or you can still do the 1994 version if you wish.) Each chapter has a “weight” that determines the number of questions from the chapter that appear on the test. This means that there is more than just GD&T; you need to be familiar with the nuances of traditional tolerancing as well as the many definitions contained in that standard. Some questions representative of the Technologist Level:

Sample question #1:

A dimension ‘not to scale’ is symbolized by:

a. placing the number in parentheses

b. placing a line under the number

c. including NTS after the number

d. italicizing the number



Sample question #2:

If a datum feature of size is applied RFS, a datum displacement is:

a. not allowed

b. allowed at MMC

c. allowed at LMC

d. allowed at the resultant condition


Sample question #3: 

When applied to planar surfaces, angularity, parallelism, and perpendicularity also control:

a. size

b. location

c. form

d. Rule #1


Sample question #4: 

Which of the following datum feature symbols is incorrect?


The GDTP process is not for everybody, but if it’s something that might interest you, contact us for some guidance or you may visit ASME’s website for more detail:

FYI — the answers are: b, a, c, and “Q,” respectively. If you got all those, send a comment and I’ll post some questions from the Senior-level test next time!


  1. It’s fun going through the questions. Would you please post more questions at the Senior-level?



  2. HI,

    Thanks for the inofrmation on sample questions. Can you please share exam pattern for GDTP? I mean questions are objective type only or some theoritical also?
    Thanks for your help.

    Thanking You,

  3. It’s hard to say exactly what pattern there might be. They are all questions that can have only one answer — in other words, there won’t be a drawing where they ask for a subjective method to tolerance something (where several people could come up with several approaches and all be correct).

    So they are meant to simply test your knowledge of the standard; in that sense I guess you could say they are theoretical. However, on the senior-level test the questions do get a little more decision-oriented: in addition to pure theory questions about knowledge of the standard, there are some questions where you must apply that knowledge to a mock part.

  4. please post some senior level exam questions

  5. Hi John,
    Are there any tips/specific literature to prepare for GDTP? Or is going through standard the best way?

    • Hi — Years ago there was a book by R. Nickolaisen that I had used to prep for the 1994 exam (I think it’s still out there: ISBN 9780791801888).
      But yes, the best prep is to systematically go through the standard and digest all of the concepts.
      Within the Y14.5.2 document’s appendix there is a “body of knowledge” that you can use as a checklist for study. And keep it mind that the exam covers more than GD&T…it also covers the early chapters of the standard, which pertain to definitions and traditional-style tolerances.

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