ISO 2768 General Tolerances: Tables, Classes, Current Status

Key Takeaways

• ISO 2768 works through a single note in the title block. One designation such as ISO 2768-m sets the permissible deviations for every linear and angular dimension that has no individual tolerance indication.^[1]

• ISO 2768-1 defines four tolerance classes for linear and angular dimensions: f (fine), m (medium), c (coarse) and v (very coarse).^[1] ISO 2768-2 defined three geometrical classes: H, K, and L.^[2]

• ISO 2768-2:1989 has been withdrawn and replaced by ISO 22081:2021.^[3] Prescribing H, K, or L for geometrical tolerances is no longer a current specification.^[4]

• ISO 2768-1:1989 remains published and was confirmed in 2022, but it is expected to be replaced by a second edition of ISO 2768, which is under publication now.^[1][5]

• Exceeding a general tolerance does not automatically reject a part. Both parts of the standard say rejection follows only when the ability of the workpiece to function is impaired.^[1][2]

Introduction

Every engineering drawing contains dimensions that do not matter much. A cover plate’s outer profile, the depth of a clearance pocket, the chamfer on a non-mating edge: putting an individual tolerance on each one clutters the drawing and wastes design time. But leaving them untoleranced is worse, because it hands the decision to whoever happens to be at the machine.

ISO 2768 solves this by defining a set of default tolerance values linked to nominal size. You put one tolerance class designation in or near the title block, and every dimension without its own tolerance indication inherits the corresponding permissible deviation.^[1]

The standard states that tolerancing on the drawing “should be complete to ensure that the elements of size and geometry of all features are controlled, i.e. nothing shall be implied or left to judgement in the workshop or in the inspection department.”^[1] General tolerances provide completeness without the need to annotate everything.

What ISO 2768 Covers (and Used to Cover)

ISO 2768 is published in two parts, and they do different jobs. Both parts were first published on the same day in November 1989, and together they canceled and replaced the older single-part ISO 2768:1973.^[1][2]

Confusingly, the first part of the standard is still active, while the second part has been withdrawn and replaced by ISO 22081:2021.^[1][2] However, although the first part remains active at the time of publication, it will be replaced soon by a new, single-part version of ISO 2768.^[1]

ISO 2768-1:1989 

The first part covers linear and angular dimensions. Its scope is “intended to simplify drawing indications and it specifies general tolerances for linear and angular dimensions without individual tolerance indications in four tolerance classes.” It applies to parts “produced by metal removal or parts that are formed from sheet metal.”^[1]

The linear dimensions it covers are: external sizes, internal sizes, step sizes, diameters, radii, distances, external radii, and chamfer heights for broken edges. It also covers angular dimensions, including angles usually not indicated such as right angles, and dimensions produced by machining assembled parts.^[1]

General tolerances do not apply to:^[1]

1. Dimensions covered by reference to other standards on general tolerances

2. Auxiliary dimensions indicated in brackets

3. Theoretically exact dimensions indicated in rectangular frames 

The third point is relevant to drawings using GD&T, because basic dimensions in boxes are not governed by the title block class.

ISO 2768-2:1989 

The withdrawn second part covered geometrical tolerances: the form, orientation, and location characteristics that a size tolerance alone does not control. Its scope specified “general geometrical tolerances to control those features on the drawing which have no respective individual indication,” in three tolerance classes.^[2]

ISO 2768-1 Tolerance Tables

These values are transcribed from the standard’s own tables. Note the tolerance class designation letters: f (fine), m (medium), c (coarse), and v (very coarse).

Table 1: Linear dimensions except broken edges

Permissible deviations in millimeters, by nominal size range.

For nominal sizes below 0.5 mm, the standard requires the deviations to be indicated adjacent to the relevant nominal size, so the general tolerance does not reach them.^[1]

Table 2: External radii and chamfer heights (broken edges)

Broken edges get their own table in which the classes pair up: fine and medium share one row of values, coarse and very coarse share another.

Table 3: Angular dimensions

Angular permissible deviations are selected by the length of the shorter side of the angle concerned, not by the angle’s magnitude. A 90° corner between a 200 mm face and a 15 mm face is read on the second row.

The standard specifies that these angular values control only the general orientation of lines or line elements of surfaces, but not their form deviations.”^[1] Angular flatness or waviness is therefore a separate problem.

Recommended reading: Press Fit Tolerance: How to Specify Interference Fits

ISO 2768-2 Geometrical Tolerance Tables

ISO 2768-2 used three classes, H, K, and L.^[2] As the tables show, H is the tightest and L the loosest. The values below are transcribed from the standard itself, which is now withdrawn but still appears on drawings issued before the change.

Straightness and flatness

For straightness the range is chosen on the length of the corresponding line. For flatness it is the longer lateral length of the surface, or the diameter of a circular surface.^[2]

Perpendicularity

The datum is the longer of the two sides forming the right angle, and the tolerance is selected on the nominal length of the shorter side. If the sides are equal, either may be the datum.^[2]

Symmetry

Class H is a single value across every length range. Class K holds one value across the first two ranges before opening up.

Symmetry general tolerances apply only where at least one of the two features has a median plane, or the axes of the two features are perpendicular to each other.^[2]

Circular run-out

Run-out tolerances take a single value per class with no length ranges at all, covering radial, axial, and any surface of revolution.^[2]

Characteristics with no table

Two geometrical characteristics are handled by rule rather than by a tolerance value:

1. Circularity equals the numerical value of the diameter tolerance, but shall in no case be greater than the respective tolerance value for circular radial run-out.”^[2]

2. Parallelism equals the size tolerance or the flatness/straightness tolerance, whichever is greater.^[2]

The standard also lists characteristics not subject to general geometrical tolerances: cylindricity, profile of any line, profile of any surface, angularity, coaxiality, positional tolerances, and total run-out.^[2]

Recommended reading: Tolerance Stack Up Analysis: Worst Case vs RSS Methods

How to Read a Specification on a Drawing

The designation is built from the class letters of each part, in order.

1. ISO 2768 identifies the standard.

2. The lowercase letter is the ISO 2768-1 class for linear and angular dimensions: f, m, c or v.

3. The uppercase letter is the ISO 2768-2 class for geometrical tolerances: H, K or L.

So a title block containing “ISO 2768-mK” means medium linear and angular tolerances with class K geometrical tolerances, although the K refers to the now-withdrawn 2768-2 so should not be used on current drawings. “ISO 2768-m” alone invokes only 2768-1.^[1][2]

Under the withdrawn 2768-2, if the general dimensional tolerances were not wanted, the lowercase letter would be simply omitted, giving a designation like “ISO 2768-K.”^[2] And where the envelope requirement applied to all single features of size, an E would be appended: “ISO 2768-mK-E.”^[2] The standard defined a single feature of size here as a cylindrical surface or two parallel plane surfaces.^[2]

You will also see the designation DIN ISO 2768 on German-origin drawings, reflecting national adoption of the ISO standard into the DIN catalog.

The State of ISO 2768 in 2026

Many circulating tolerance references still present ISO 2768-2 2 as though it were current.

However, ISO 2768-2:1989 is withdrawn. The ISO catalog lists its status as Withdrawn at stage 95.99, with the note “New version available: ISO 22081:2021.”^[2] 

ISO 22081:2021, titled Geometrical product specifications (GPS), Geometrical tolerancing, General geometrical specifications and general size specifications, states in its foreword that it “cancels and replaces ISO 2768-2:1989, which has been technically revised.”^[3] It was reviewed and confirmed in 2026, so it is the current document.^[3]

The main changes to the withdrawn ISO 2768-2 found in the current ISO 22081 are:^[3]

• Addition of tools to specify a general geometrical specification and general size specification

• Clarification of rules for application of general geometrical specification and general size specification 

Karel Petr of the Czech Technical University in Prague explained in a 2024 conference paper on ISO 22081 that “it is no longer possible to prescribe accuracy classes for geometrical tolerances, H, K, or L.”^[4]

Petr identifies three reasons the older approach was retired:^[4]

1. Incompatibility with the ISO Geometrical Product Specifications framework, specifically the confusion of “distance” with “size”: he argues a distance “should never be tolerated, i.e., it should not carry limit deviations”

2. Measurement: such a distance “is not correctly measurable and evaluated on CMMs or scanners,” which now dominate inspection

3. The move to drawing-less documentation and 3D annotation models, where functional specifications are in the model rather than on a 2D sheet

ISO 2768-1:1989 is still published, and was last reviewed and confirmed in 2022.^[1] But it sits at stage 90.92, “International Standard to be revised,” and its catalog page carries the note “Expected to be replaced by ISO 2768 within the coming months.”^[1]

ISO lists this forthcoming edition of ISO 2768, retitled Geometrical product specifications (GPS), Dimensional tolerancing, Tolerance limits for general specification of linear and angular sizes, at stage 60.00, “International Standard under publication,” with the note “Will replace ISO 2768-1:1989.”^[5] 

Both parts have also moved technical committee. The 1989 editions were prepared by ISO/TC 3, Limits and fits.^[1][2] The current catalog entries, the forthcoming edition, and ISO 22081 all sit with ISO/TC 213, Dimensional and geometrical product specifications and verification.^[1][3][5]

Choosing a Tolerance Class

The standard recommends that choice of tolerance class be based on manufacturer capability as well as part requirements: “When selecting the tolerance class, the respective customary workshop accuracy has to be taken into consideration.”^[1]

For its part, a shop should “find out by measurements what its customary workshop accuracy is,” accept only drawings whose general tolerances are equal to or greater than that accuracy, and “check by sampling that its customary workshop accuracy does not deteriorate.”^[1]

In a  worked example, the annex to 2768-1 describes a 35 mm diameter feature made in a workshop of customary medium accuracy, where the general tolerance value of ±0.3 mm “would be quite adequate,” noting that specifying ±1 mm “would be of no benefit in this particular workshop.”^[1]

Two rules of thumb may be helpful:

1. Class m is commonly used as the default on general CNC machining work, with the coarser classes applied to sheet metal fabrication and similar processes, though the standard itself sets no such mapping and leaves the choice to measured workshop capability.^[1]

2. Where a feature genuinely needs a tighter tolerance, the standard states that it should carry an individual tolerance adjacent to the dimension, which “falls outside the scope of general tolerances.”^[1]

Applicable processes and industries

ISO 2768-1 applies “to the dimensions of parts that are produced by metal removal or parts that are formed from sheet metal,” which puts CNC machining and sheet metal fabrication squarely at its center.^[1] ISO 2768-2 was narrower still, applying “mainly to features which are produced by removal of material.”^[2]

Extending it beyond those processes is allowed but conditional. ISO 2768-1 notes that its tolerances “may be suitable for use with materials other than metal.”^[1] So for anyone reaching for ISO 2768 on injection molding drawings, nothing forbids it, but the tolerance range in these tables was calibrated to machining and sheet metal capability.

Because the standard names no specific sectors, you will find general tolerance classes on technical drawings across aerospace, automotive, and medical devices work. The class still has to be justified by measured capability in every case, and any interface that needs fine tolerances requires an individual callout regardless of industry.^[1]

ISO 2768 Compared With ASME Y14.5

These two standards are often set against each other, but they are not the same kind of document.

ISO 2768 is a table of default permissible deviations invoked by a title block note. ASME Y14.5-2018 (reaffirmed 2024) is a geometric dimensioning and tolerancing language that “establishes symbols, rules, definitions, requirements, defaults, and recommended practices for stating and interpreting GD&T and related requirements for use on engineering drawings, models defined in digital data files, and in related documents.”^[6]

The two are complementary rather than competing. ISO 2768-1 notes that where a feature needs a smaller tolerance than the general class allows, that tolerance “should be indicated adjacent to the relevant nominal dimension(s).”^[1] A drawing can therefore carry ISO 2768-m in the title block and full GD&T feature control frames on important interfaces.

Recommended reading: GD&T Explained: Symbols, Datums, and Tolerances

Conclusion

ISO 2768 remains the fastest way to make technical drawings complete without annotating every dimension, and its tables are still the reference most machine shops work to for CNC machining and sheet metal work. The four linear classes and the three defunct geometrical classes cover the great majority of parts produced by machining and sheet metal work.

Frequently Asked Questions

What does ISO 2768-mK mean?

Medium general tolerances for linear and angular dimensions per ISO 2768-1, combined with class K general geometrical tolerances per the withdrawn ISO 2768-2.^[1][2]

Is ISO 2768 still valid?

Partly. ISO 2768-1:1989 is still published and was confirmed in 2022, though ISO expects to replace it with a second edition that is currently under publication.^[1] ISO 2768-2:1989 is withdrawn and was replaced by ISO 22081:2021.^[2]

What are the four ISO 2768 tolerance classes?

f (fine), m (medium), c (coarse), and v (very coarse), defined in ISO 2768-1 for linear and angular dimensions.^[1]

What is the difference between ISO 2768-1 and ISO 2768-2?

Part 1 gives permissible deviations for linear and angular dimensions such as external sizes, diameters, distances, external radii, and chamfer heights. Part 2 gave general geometrical tolerances for straightness and flatness, perpendicularity, symmetry, and circular run-out.^[1][2]

Does ISO 2768 cover cylindricity?

No. ISO 2768-2 states that general tolerances on cylindricity are not specified, and lists cylindricity among the characteristics general geometrical tolerances do not apply to.^[2]

What tolerance is ISO 2768-m for a 50 mm dimension?

±0.3 mm. A 50 mm nominal size falls in the “over 30 up to 120” range, where class m gives ±0.3 mm.^[1]

Is a part rejected if it exceeds the general tolerance?

Not automatically. The standard says exceeding a general tolerance should lead to rejection only if the ability of the workpiece to function is impaired.^[1]

Is ISO 2768 a CNC machining tolerance standard?

It is the general tolerance standard most often applied to CNC machined parts, because its scope covers parts produced by metal removal.^[1] But it is not specific to CNC machining. It sets default permissible deviations for any dimension on technical drawings that lacks an individual tolerance indication, and a critical CNC machining tolerance should still be called out individually.^[1]

What replaced ISO 2768-2?

ISO 22081:2021, which gives rules for general geometrical specifications and general size specifications defined according to ISO 8015:2011.^[3]

References

[1] International Organization for Standardization. ISO 2768-1:1989: General tolerances—Part 1: Tolerances for linear and angular dimensions without individual tolerance indications. Geneva: ISO; confirmed 2022.

[2] International Organization for Standardization. ISO 2768-2:1989: General tolerances—Part 2: Geometrical tolerances for features without individual tolerance indications. Geneva: ISO; withdrawn.

[3] International Organization for Standardization. ISO 22081:2021: Geometrical product specifications (GPS)—Geometrical tolerancing—General geometrical specifications and general size specifications. Geneva: ISO; confirmed 2026.

[4] Petr K. Application and explanation of general geometrical tolerances according to ISO 22081. In: Proceedings of the 62nd International Conference of Machine Design Departments (ICMD 2022). Atlantis Highlights in Engineering. Vol. 28. Atlantis Press; 2024.

[5] International Organization for Standardization. ISO 2768: Edition 2. Geneva: ISO; under development.

[6] American Society of Mechanical Engineers. ASME Y14.5: Dimensioning and tolerancing. 2018 ed. New York: ASME; reaffirmed 2024.