Model-Based Definition > Model-Based Definition > Creating Various Annotation Types > Tolerances > Working with Dimensional Tolerances > Dimensional Tolerance Basics > About Dimensional Tolerances
About Dimensional Tolerances
When you design a part, you specify allowable variations in size referred to as dimensional tolerances. All dimensions are controlled by tolerances (except basic dimensions, which, for the purpose of reference, are considered exact).
In Creo Parametric, you can express dimensional tolerances in one of two forms: general or individual. General tolerances apply to those dimensions that appear in a nominal format, that is, without tolerances. They are displayed in a tolerance table. Individual tolerances specify individual dimensions.
You can set the tolerance standard as ANSI or ISO and drive dimensional tolerances using a set of tolerance tables.
When you switch from ISO to ANSI, the system assigns the ANSI tolerances based on the number of digits in the nominal dimension and deletes the tolerance table reference.
When you switch from ANSI to ISO, a set of tolerance tables drives the ISO-standard tolerances.