GDTP stands for Geometric Dimensioning and Tolerancing Professional. It is a certification program offered by the American Society of Mechanical Engineers (ASME) that verifies an individual's competence in understanding and applying the principles of Geometric Dimensioning and Tolerancing (GD&T). GD&T is an essential language used for clear communication in manufacturing, ensuring that designs are manufactured as intended.

ASME's Y14.5 Standard serves as the authoritative guideline for GD&T, and GDTP certification is based on either the 1994 or 2009 revisions of this standard, including its appendices and the application of its principles and practices . The certification program offers two levels of certification: Technologist and Senior.

Technologist Level Certification indicates proficiency in understanding the rules, definitions, principles, and meanings of GD&T symbols and modifiers, as well as performing calculations associated with GD&T. Technologists also apply GD&T principles to functional gaging activities.

Senior Level Certification encompasses a deeper understanding of GD&T symbols, modifiers, and relationships, and the ability to make proper selections to document the product design intent. Senior-level professionals also perform calculations for geometric requirements and apply appropriate geometric control symbols, modifiers, and datum references. They further apply GD&T principles to manufacturing, quality control, verification processes, and functional gaging activities.