Injection-molded plastic part tolerances are primarily driven by material shrinkage and nominal dimension, not the molding process alone. Different resins shrink at different rates as they cool, so the same nominal dimension can require a tighter or looser tolerance depending on the material you choose.
Tolerance standards give you a consistent way to account for this. Based on PLASTICS/SPI standards and aligned with ISO 20457, they define Commercial and Fine tolerance values for every feature type, from linear dimensions to hole diameter, across a wide range of engineering resins.
Download the Injection Molding Tolerances Calculator to instantly look up Commercial and Fine tolerance values for any nominal dimension, in inches or millimeters, across 15 engineering resins including ABS, PC, PA (Nylon), POM, and PP.
Read this article to learn more about injection molding tolerances.
