DIN ISO 2768 defines general tolerances for all dimensions that carry no individual tolerance indication in a technical drawing. Part 1 governs linear and angular dimensions in the tolerance classes f, m, c and v, part 2 governs form and position tolerances in the classes H, K and L. The most common drawing note is DIN ISO 2768-mK and means: dimensional tolerances according to class m (medium), form and position tolerances according to class K. On this page you will find all tolerance tables of both parts of the standard and a calculator that determines the permissible limit deviations for your nominal size directly.
Calculating general tolerances: interactive tolerance calculator according to DIN ISO 2768
Enter your nominal size and select the dimension type and tolerance class. The calculator immediately shows the permissible deviation, the minimum size and the maximum size. It covers both parts of the standard: linear dimensions, radii, chamfers and angles according to DIN ISO 2768-1 as well as straightness, flatness, perpendicularity, symmetry and run-out according to DIN ISO 2768-2.
Tolerance calculator according to DIN ISO 2768
Calculate limit deviations for linear, angular, form and position tolerances directly. Values according to DIN ISO 2768-1 and DIN ISO 2768-2.
This tolerance calculator is based on the verified values of DIN ISO 2768-1 and DIN ISO 2768-2.
In practice, tolerance class m (medium) is used most often, as it is sufficient for most standard components. For higher requirements, for example in toolmaking or for fits, class f (fine) is recommended. Classes c (coarse) and v (very coarse) are used for lower accuracy requirements, for example in structural steelwork or in the machining of castings.
What are general tolerances according to ISO 2768?
Definition and significance of ISO 2768
ISO 2768 is an international standard that defines the permissible deviations in dimensional, form and position tolerances. It serves to simplify design drawings by no longer requiring individual tolerance specifications for certain dimensions: the corresponding deviations are covered globally by the standard. General tolerances are particularly important for components where a certain dimensional deviation is technically uncritical. This simplifies the production process, reduces costs and at the same time improves quality assurance.
At GOBA we manufacture stamped and bent parts as well as custom products reliably to DIN ISO 2768.
Difference between ISO 2768 and DIN ISO 2768
While the designation DIN ISO 2768 refers to the German version of the international standard, ISO 2768 is the original international version. In content, both are identical.
Areas of application for general tolerances
ISO 2768 is applied in metalworking, mechanical engineering and wherever technical drawings are created, for example for molded parts made of insulating materials. It simplifies dimensioning because a specific tolerance does not have to be specified for each dimension.
What does DIN ISO 2768-mK mean?
The note DIN ISO 2768-mK combines one tolerance class from each part of the standard. The lower-case letter stands for the dimensional tolerances according to part 1, the upper-case letter for the form and position tolerances according to part 2:
- m stands for the medium tolerance class for linear and angular dimensions. A dimension of 100 mm may thus deviate by ±0.3 mm.
- K stands for the medium class of form and position tolerances, that is straightness, flatness, perpendicularity, symmetry and run-out. A surface with an edge length of 200 mm may thus show a flatness deviation of 0.4 mm.
Both specifications apply independently of each other. Anyone checking a drawing with the note 2768-mK therefore needs both sets of tables: the dimensional tolerances from part 1 and the form and position tolerances from part 2. You will find both in full further down this page. Other common combinations are 2768-fH for precision parts and 2768-cL for coarse welded structures.
How is the ISO 2768 standard structured?
The standard is divided into two parts:
ISO 2768-1: Tolerances for length and angular dimensions
This part governs tolerances for linear dimensions (for example lengths, widths), for broken edges (radii of curvature and chamfer heights) and for angular dimensions. Tolerances depend on the nominal size range and are divided into four classes:
- f (fine)
- m (medium)
- c (coarse)
- v (very coarse)
Depending on the application and the desired precision, the appropriate tolerance class is selected.
ISO 2768-2: Geometric tolerances
This part defines tolerances for geometric properties such as straightness, flatness, perpendicularity, symmetry and run-out in the three classes H, K and L. Internationally, part 2 was withdrawn in 2021 and replaced by ISO 22081, but it remains binding in existing drawings. Details can be found below in the section on ISO 22081.
Which tolerance classes exist in ISO 2768?
Tolerance table for linear dimensions according to DIN ISO 2768-1
The limit deviations apply to all linear dimensions without an individual tolerance indication, in mm:
| Nominal size range (mm) | f (fine) | m (medium) | c (coarse) | v (very coarse) |
|---|---|---|---|---|
| 0.5 to 3 | ±0.05 | ±0.1 | ±0.2 | - |
| over 3 to 6 | ±0.05 | ±0.1 | ±0.3 | ±0.5 |
| over 6 to 30 | ±0.1 | ±0.2 | ±0.5 | ±1.0 |
| over 30 to 120 | ±0.15 | ±0.3 | ±0.8 | ±1.5 |
| over 120 to 400 | ±0.2 | ±0.5 | ±1.2 | ±2.5 |
| over 400 to 1000 | ±0.3 | ±0.8 | ±2.0 | ±4.0 |
| over 1000 to 2000 | ±0.5 | ±1.2 | ±3.0 | ±6.0 |
| over 2000 to 4000 | - | ±2.0 | ±4.0 | ±8.0 |
For nominal sizes below 0.5 mm the standard does not provide a general tolerance, these dimensions must be toleranced directly at the dimension.
Tolerance table for radii and chamfer heights
Separate, considerably wider limit deviations apply to broken edges, that is radii and chamfers. Classes f and m as well as c and v each share the same values:
| Nominal size range (mm) | f and m | c and v |
|---|---|---|
| 0.5 to 3 | ±0.2 | ±0.4 |
| over 3 to 6 | ±0.5 | ±1.0 |
| over 6 | ±1.0 | ±2.0 |
Tolerance table for angular dimensions
For angular dimensions, the permissible deviation depends on the length of the shorter leg. Classes f and m share the same values:
| Shorter leg (mm) | f and m | c (coarse) | v (very coarse) |
|---|---|---|---|
| up to 10 | ±1° | ±1°30' | ±3° |
| over 10 to 50 | ±0°30' | ±1° | ±2° |
| over 50 to 120 | ±0°20' | ±0°30' | ±1° |
| over 120 to 400 | ±0°10' | ±0°15' | ±0°30' |
| over 400 | ±0°5' | ±0°10' | ±0°20' |
Selecting the right tolerance class
The choice of tolerance class depends on the function of the component. Anyone who tolerances too finely across the board pays for manufacturing and inspection effort the component does not need. This assignment has proven itself in practice:
| Application | Recommended class | Reasoning |
|---|---|---|
| Standard components in mechanical engineering, housings, brackets | m (medium) | Balanced ratio of manufacturing effort and accuracy |
| Fits, toolmaking, gauges | f (fine) | Tight limit deviations for functional surfaces, higher inspection effort |
| Welded structures, structural steelwork | c (coarse) | Large components with thermal distortion, tight tolerances uneconomical |
| Raw castings, coarse blanks | v (very coarse) | Raw parts are reworked, the final dimension is created later |
Tolerance tables according to DIN ISO 2768-2: form and position tolerances
Part 2 of the standard defines general tolerances for straightness, flatness, perpendicularity, symmetry and run-out, each in the classes H, K and L. Anyone checking the drawing note 2768-mK will find the values for the K here. All values in mm.
Straightness and flatness
For straightness, the length of the line is decisive, for flatness the longer side of the surface or the diameter:
| Nominal size range (mm) | H | K | L |
|---|---|---|---|
| up to 10 | 0.02 | 0.05 | 0.1 |
| over 10 to 30 | 0.05 | 0.1 | 0.2 |
| over 30 to 100 | 0.1 | 0.2 | 0.4 |
| over 100 to 300 | 0.2 | 0.4 | 0.8 |
| over 300 to 1000 | 0.3 | 0.6 | 1.2 |
| over 1000 to 3000 | 0.4 | 0.8 | 1.6 |
Perpendicularity
The length of the shorter leg is decisive:
| Shorter leg (mm) | H | K | L |
|---|---|---|---|
| up to 100 | 0.2 | 0.4 | 0.6 |
| over 100 to 300 | 0.3 | 0.6 | 1.0 |
| over 300 to 1000 | 0.4 | 0.8 | 1.5 |
| over 1000 to 3000 | 0.5 | 1.0 | 2.0 |
Symmetry
The larger of the two mutually symmetrical dimensions is decisive:
| Nominal size range (mm) | H | K | L |
|---|---|---|---|
| up to 100 | 0.5 | 0.6 | 0.6 |
| over 100 to 300 | 0.5 | 0.6 | 1.0 |
| over 300 to 1000 | 0.5 | 0.8 | 1.5 |
| over 1000 to 3000 | 0.5 | 1.0 | 2.0 |
Circular and axial run-out
For run-out tolerances, a fixed value applies per class, independent of the nominal size:
| Tolerance class | Run-out tolerance (mm) |
|---|---|
| H | 0.1 |
| K | 0.2 |
| L | 0.5 |
The standard does not define separate tables for roundness and parallelism. The roundness tolerance corresponds to the numerical value of the diameter tolerance, parallelism is limited by the dimensional tolerance and the flatness or straightness tolerance.
How are tolerances according to ISO 2768 indicated in technical drawings?
Correct specification of general tolerances
General tolerances are indicated in technical drawings by a note such as: General tolerances according to DIN ISO 2768-mK
Here:
- m stands for the tolerance class of dimensional deviation according to part 1
- K stands for the class of form and position tolerances according to part 2
Examples of tolerance specifications in drawings
A typical note in a drawing reads: Dimensions in mm. Tolerances according to DIN ISO 2768-mK. The note is usually placed in the title block of the drawing and applies to all dimensions without their own tolerance indication. Individually toleranced dimensions always take precedence over the general tolerance.
General tolerances for insulating materials and stamped parts
ISO 2768 is worded in a material-neutral way, but it originated in metal machining. For flexible electrical insulating materials such as polyester film, aramid paper, pressboard or vulcanized fibre, applying the standard without reflection reaches its limits. Three points deserve particular attention:
- Soft and limp materials deform under the measuring force. The measuring equipment and the measuring method are therefore part of the tolerance agreement, otherwise supplier and customer measure different values on the same part.
- Hygroscopic materials such as pressboard and vulcanized fibre change their dimensions with humidity, plastic films expand with temperature. Tight tolerance classes can only be meaningfully verified for these materials with reference to a standard climate.
- Form and position tolerances according to part 2, such as flatness, require dimensionally stable workpieces. For a 0.19 mm thin insulating film, a flatness check according to 2768-2 is not meaningful.
In production at GOBA this means in concrete terms: In contract slitting we hold width tolerances of ±0.1 mm for web widths from 5 to 1,600 mm, considerably tighter than class f of the general tolerance. We manufacture stamped and bent parts according to DIN ISO 2768, and for functional dimensions such as hole spacings or fits we agree tighter individual tolerances directly at the drawing position. Our recommendation for drawings of insulating parts: class m as the basis, class f only where the function demands it, and for soft materials define the measuring method at the same time. We support you in the design process as part of our consulting services.
What is the difference between ISO 2768 and the new ISO 22081?
Status of the two parts of the standard
The two parts of ISO 2768 have a different status today. Part 1 with the dimensional tolerances is still valid. Part 2 with the form and position tolerances was withdrawn internationally in 2021 and replaced by ISO 22081, which has been available in the German standards system as DIN EN ISO 22081 since October 2022.
What ISO 22081 does differently
In contrast to ISO 2768-2, ISO 22081 does not contain tables of numerical values. The designer defines the general geometrical specifications and indicates them on the drawing. Because German industry thus lacked the familiar table values, the DIN standards committee published DIN 2769 as a national supplement, whose values are based on the old DIN ISO 2768.
For practice this means: existing drawings with the note DIN ISO 2768 remain binding, because the drawing note determines the applicable standard. For new designs, either switching to ISO 22081 with DIN 2769 or a dated reference to the old standard is recommended so that the reference version remains unambiguous.
How are the tolerance tables according to ISO 2768 applied in practice?
Step-by-step guide
- Check the drawing: are there specific tolerance specifications? If not, the general tolerances apply.
- Determine the nominal size: what is the dimension of the component?
- Read the tolerance class from the drawing note, for example m and K for 2768-mK.
- Read the permissible deviation from the appropriate table or determine it with the calculator above.
Avoiding common errors in application
- Choosing the class too finely across the board and thus generating unnecessary manufacturing costs
- Specifying 2768-mK but only checking the dimensional tolerances and forgetting the K
- Letting functional dimensions run under the general tolerance instead of tolerancing them individually
- Disregard of special requirements for form and position tolerances
- Incorrect transfer of tolerances onto manufacturing drawings
Which advantages does the use of general tolerances according to ISO 2768 offer?
- Designers save time because they do not have to tolerance uncritical dimensions individually
- Appropriate tolerance allocation prevents unnecessarily tight dimensional requirements and reduces production costs
- Standardised tolerances simplify production, communication with suppliers and the final inspection of components
GOBA conclusion: class m as the base, functional dimensions toleranced individually
For insulating parts, most drawings carry the note DIN ISO 2768-mK. At a nominal size of 100 mm, class m permits a deviation of ±0.3 mm, which is sufficient for any contour that does not form a fit. Only dimensions with a function belong in a tighter tolerance: the fitting dimension the part engages with, and the hole spacing for a screw or rivet. With soft insulating materials, two further details belong on the drawing, because papers and laminates absorb moisture and change their dimensions with it: the measuring method and the reference climate. A flatness check to 2768-2 on a 0.19 mm film yields no meaningful result. Anyone sourcing stamped and bent parts to drawing settles both before sampling. Part 2 of the standard was withdrawn internationally in 2021 and replaced by ISO 22081, yet the note 2768-mK remains common on current drawings.
