The full table includes separate columns for:
Unlike metals, plastic dimensions are highly dynamic. ISO 20457 determines tolerance groups based on four major variables:
The ISO 20457 tolerance table, found within the standard’s PDF, is a cornerstone of modern geometric product specification. It translates the abstract concept of “general tolerance” into specific, actionable numbers for linear dimensions, angles, flatness, straightness, perpendicularity, and runout. By organizing these values into four clear classes (f, m, c, v), the standard balances manufacturing economy with functional assurance. For any design engineer or manufacturing professional, understanding how to read and apply the tables in ISO 20457 is not a niche skill—it is a fundamental practice that turns a drawing into a reliable, producible product.
The standard provides a framework for specifying tolerances that balance the need for precision with the practical limitations of manufacturing processes.
ISO 20457 places heavy emphasis on injection molded fittings. The tolerances here are tighter than for pipes because molds are machined to high precision. iso 20457 tolerance table pdf
Key structure of the tolerance table (typical elements)
The tolerance tables are split based on what is being measured. The two most common tables you will encounter are:
The standard classifies manufacturing accuracy into . Each group represents a specific balance between the complexity of the production process and the inherent properties of the plastic material. Tolerance Group Accuracy Classification Typical Application Examples TG1 to TG3 Extreme Precision Micro-optics, medical devices, ultra-tight aerospace gears. TG4 High Precision
To help me tailor the recommendation, could you tell me a bit more about your project? The full table includes separate columns for: Unlike
To create a unified global standard for these variances, the International Organization for Standardization introduced ("Plastics molded parts — Tolerances and acceptance conditions"). This standard replaced the older German standard DIN 16742 in 2018.
The standard is part of the broader ISO GPS (Geometrical Product Specifications) system. The GPS "matrix model" provides a set of rules and tools for the specification of geometry, and ISO 20457 is fully integrated within this framework.
Standard measurement temperature (usually 23°C) and humidity (50% RH).
📐 Tolerance Class TG6: The Most Common Injection Molding Standard TOLERANCES By organizing these values into four clear classes
To ensure your manufacturer interprets your designs correctly, follow these documentation standards on your engineering prints:
ISO 20457:2018 was developed to serve as the true international successor to DIN 16901. It broadened the scope of tolerancing while introducing a more refined and objective system. The new standard introduced , a significant increase from the six tolerance groups (110–160) used in the old DIN 16901 system. This expansion provides designers with greater flexibility and control when specifying precision levels for their parts.
The standard acknowledges that plastics are viscoelastic. Their final dimensions depend on: