Abstract Dimensioning and tolerancing are inter-related tasks; the validity of the tolerance representation model is dependent on the dimension model. Validation of tolerances is necessary at input and also after any changes of the dimension scheme. This paper presents a computational model for validating the dimensioning scheme and tolerance specifications compatible with dimensioning and tolerancing practice. Validation is implemented through a dimension and tolerance graph. Constrained entities are combined into progressively expanding clusters, which can be used to represent datum reference frames (DRFs), constraint groups of geometric entities, patterns, or the entire part. Validation of all dimensioning and tolerancing relations is performed using the concept of control frames, theoretical dimensions and general rules for forming clusters. The tolerance validation method proposed here supports all tolerance classes defined in the ISO/ANSI/ASME standards, as well as DRFs and special pattern and profile entity relations.