ISO 22081:2021

Overview

ISO 22081:2021 - "Geometrical product specifications (GPS) - Geometrical tolerancing - General geometrical specifications and general size specifications" - defines rules for creating and interpreting general geometrical specifications and general size specifications used in technical product documentation (TPD). It provides a structured way to apply common tolerances across many integral features of a part (thereby reducing repetitive indication) while clarifying limits: it applies only to integral features (including features of size), linear or angular size dimensions, and does not cover derived features, integral lines, or non-linear/non-angular dimensions.

Key topics and requirements

• Scope and applicability
  • Applies only to integral features as defined by ISO 17450-1.
  • Excludes derived features, integral lines, and dimensions other than linear or angular (see ISO 14405 series).
• Indication in TPD
  • General specifications must be clearly indicated (e.g., wording “General tolerances” with a reference to ISO 22081) in or near the title block or product definition dataset.
  • Tolerance values can be single or variable (dependent on feature size or distance to the datum system using TEDs).
• Types of general specifications
  • Two main types: general geometrical specifications and general size specifications (linear or angular).
  • Rule: only the specification types listed in the standard’s tables (Tables 1 & 2) may be used to define general specifications.
• General geometrical specification format
  • The standard requires the general geometrical specification to be indicated with a surface profile characteristic.
• Applicability exceptions
  • General specs do not apply where an integral feature is:
    • specified by an individual or general size specification;
    • specified by an individual geometrical specification (or its derived feature);
    • used as a datum in the datum system referenced by the general specification;
    • represented only in simplified form (e.g., threads, fillets not modeled in CAD).
• Designer responsibilities
  • Ensure functional requirements are captured, appropriate features are specified, and the overall part specification is complete and unambiguous.

Applications

• Streamlines drawings and 3D CAD datasets by applying consistent tolerances across multiple similar features.
• Useful for mechanical designers, CAD modelers, manufacturing and quality engineers, and technical drafters to:
  • reduce annotation clutter in TPD,
  • standardize tolerances across families of features,
  • support inspection planning and contract requirements with clear general tolerancing rules.
• Supports both 2D drawing conventions and 3D model-based definition workflows (see ISO 16792 for CAD attachment rules).

Related standards

• ISO 8015 (fundamental GPS principles)
• ISO 17450‑1 / ISO 17450‑2 (GPS model and concepts)
• ISO 14405 series (size definitions)
• ISO 5459, ISO 1101 (geometrical specification elements)
• ISO 14638, ISO 14253‑1, ISO 22432, ISO 25378 (GPS system context)

For implementation, reference the full ISO 22081:2021 text and consult your national standards body or ISO/TC 213 guidance.