— The tolerance design directly influences the functionality of products and production costs. Tolerance synthesis is a procedure that distributes assembly tolerances between components. To ensure that the selected components and its tolerances give the assembly tolerance less than a desired value, worst-case analysis is commonly used. Even though the worst-case analysis is used, there is still a probability that a product performance is out of its tolerance. Moreover, using the worst-case analysis, some assumptions need to be realized. The first is, nominal value of components and assembly are at the desirable values. The second is, left-sided and right-sided tolerances are symmetric in both components and assembly. Use of probabilistic tolerance synthesis may relax those assumptions and quantify the loss due to falling out of assembly limit. This paper then gives a comparative study of worst-case and probabilistic tolerance syntheses. A numerical example is used to illustrate the u...