ISO 2768 is the international standard that defines general tolerances for linear and angular dimensions on technical drawings when no specific tolerances are stated. It helps ensure consistent interpretation of dimensions, reduces ambiguity, and avoids unnecessary over-specification in manufacturing and engineering.
ISO 2768 is a product and drawing standard, not a management system, and it is widely used across mechanical engineering, machining, fabrication, and manufacturing.
What is ISO 2768?
ISO 2768 is published by the International Organization for Standardization. It provides default tolerance limits that apply automatically when drawings reference ISO 2768 and individual dimensions are left untoleranced.
The standard is commonly referenced with a note such as: “General tolerances ISO 2768-m”
What does ISO 2768 cover?
ISO 2768 is split into two main parts:
ISO 2768-1 – General tolerances for linear and angular dimensions
Covers:
- Linear dimensions (length, width, diameter, thickness)
- Angular dimensions
- External and internal radii
- Chamfer heights
ISO 2768-2 – Geometrical tolerances
Covers:
- Straightness
- Flatness
- Parallelism
- Perpendicularity
- Symmetry
- Circular run-out
Together, these parts define how precise parts must be when no individual tolerance is specified.
Tolerance classes explained (ISO 2768-1)
ISO 2768-1 defines four tolerance classes, allowing designers to balance precision and cost:
| Class | Meaning | Typical use |
|---|---|---|
| f | Fine | High-precision components |
| m | Medium | General engineering (most common) |
| c | Coarse | Fabrication and welded parts |
| v | Very coarse | Rough or non-critical parts |
The chosen class applies across the entire drawing unless otherwise specified.
Geometrical tolerance classes (ISO 2768-2)
ISO 2768-2 defines three geometrical tolerance classes:
| Class | Description |
|---|---|
| H | Fine geometrical tolerances |
| K | Medium geometrical tolerances |
| L | Coarse geometrical tolerances |
These control shape and positional accuracy where no explicit GD&T values are given.
Why ISO 2768 is important
Using ISO 2768 helps organisations:
- Avoid missing or ambiguous tolerances
- Reduce drawing complexity
- Prevent disputes between design and manufacturing
- Control production costs
- Improve consistency across suppliers
It allows designers to specify only critical tolerances, relying on ISO 2768 for everything else.
Who is ISO 2768 for?
ISO 2768 is widely used by:
- Mechanical and manufacturing engineers
- CAD designers and draughtspersons
- Machining and fabrication workshops
- Toolmakers and component suppliers
- Quality and inspection teams
It is particularly common in subcontract manufacturing and international supply chains.
ISO 2768 vs fully toleranced drawings
| ISO 2768 | Fully toleranced drawings |
|---|---|
| Default tolerances applied | Every dimension specified |
| Faster drawing creation | More detailed drafting |
| Lower risk of over-tolerance | Higher risk of unnecessary cost |
| Requires correct class selection | Maximum design control |
ISO 2768 is most effective when combined with explicit tolerances on critical features.
How ISO 2768 is applied on drawings
ISO 2768 is typically applied by:
- Adding a general tolerance note to the title block
- Selecting a tolerance class (for example, ISO 2768-mK)
- Applying specific tolerances only where tighter or looser control is needed
Example notation: ISO 2768-mK
(m = medium linear tolerances, K = medium geometrical tolerances)
Is ISO 2768 certifiable?
No. ISO 2768 cannot be certified.
It is a technical drawing standard used in design and manufacturing. Products may be inspected against ISO 2768 tolerances, but organisations are not certified to it.
Benefits of using ISO 2768
Organisations that use ISO 2768 effectively often achieve:
- Clearer communication between design and production
- Reduced drawing errors and rework
- More predictable manufacturing outcomes
- Lower production and inspection costs
- Improved supplier consistency
Correct use helps balance functionality, quality, and cost.
Common misunderstandings about ISO 2768
- “ISO 2768 applies automatically” – it must be referenced on the drawing
- “Tighter tolerances are always better” – they increase cost and risk
- “ISO 2768 replaces GD&T” – it complements it
- “One class fits all parts” – class selection is critical
Understanding these points prevents misuse and quality issues.
How ISO 2768 fits with other standards
ISO 2768 is commonly used alongside:
- ISO GPS (Geometrical Product Specifications) standards
- ISO 1101 (geometrical tolerancing)
- ISO 9001 (quality management systems)
- Industry-specific drawing and inspection standards
It supports consistent dimensional control within wider quality systems.
Next steps
If you are using or specifying ISO 2768:
- Choose tolerance classes appropriate to function and manufacturing method
- Apply ISO 2768 notes clearly on drawings
- Specify critical dimensions explicitly
- Ensure suppliers understand the referenced classes
- Align inspection methods with ISO 2768 limits
ISOcertified.net provides guidance on ISO technical standards, including ISO 2768, how to apply general tolerances correctly, and how dimensional standards support efficient, high-quality manufacturing.