ISO 2768 is the ISO standard for general tolerances: the deviations that apply to every dimension on a drawing that has no tolerance written next to it. Part 1 (ISO 2768-1:1989) covers linear and angular dimensions in four classes, f, m, c and v; part 2 (ISO 2768-2:1989) covered geometrical tolerances in three classes, H, K and L, and was withdrawn in 2021.
What does ISO 2768 cover?
A general tolerance saves the designer from tolerancing every dimension. One note in or near the title block, such as "ISO 2768-m", sets the permissible deviation for all untoleranced sizes, and only the dimensions that matter for function carry an individual tolerance.
ISO 2768-1 applies to linear dimensions (external and internal sizes, steps, diameters, radii, distances), to external radii and chamfer heights, and to angular dimensions. It is written for parts made by metal removal and formed from sheet metal. It does not apply to dimensions that carry their own tolerance, to auxiliary dimensions in brackets or to theoretically exact dimensions in a frame.
ISO 2768-2 added general tolerances for form and position: straightness, flatness, perpendicularity, symmetry and circular run-out. Its status has changed, see the section on validity below.
What are the ISO 2768-1 tolerances for linear dimensions?
Find the range that contains the nominal size, then read the deviation in the column of the class on the drawing. The ranges are "over … up to and including", so 30 mm belongs to 6–30 and 30.1 mm to 30–120.
Table 1. Permissible deviations for linear dimensions, ISO 2768-1, mm
| Nominal size | 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 |
| 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 | ±4 |
| over 1000 to 2000 | ±0.5 | ±1.2 | ±3 | ±6 |
| over 2000 to 4000 | — | ±2 | ±4 | ±8 |
Source: ISO 2768-1:1989, Table 1. For nominal sizes below 0.5 mm the deviation is written next to the dimension.
Worked example: a 50 mm length on a drawing marked ISO 2768-m lies in the range over 30 up to 120 mm, so any measured value from 49.7 mm to 50.3 mm conforms. The same length in class f would have to measure 49.85 mm to 50.15 mm.
Which tolerances apply to radii, chamfers and angles?
External radii and chamfer heights have their own, wider table, because a 0.2 mm deviation on a 1 mm chamfer rarely affects function.
Table 2. Permissible deviations for external radii and chamfer heights, ISO 2768-1, mm
| Nominal size | f and m | c and v |
|---|---|---|
| 0.5 to 3 | ±0.2 | ±0.4 |
| over 3 to 6 | ±0.5 | ±1 |
| over 6 | ±1 | ±2 |
Source: ISO 2768-1:1989, Table 2.
Angular deviations depend on the length of the shorter leg of the angle, not on the angle itself.
Table 3. Permissible deviations for angular dimensions, ISO 2768-1, by length of the shorter side in mm
| Shorter side | f and m | c | v |
|---|---|---|---|
| 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′ |
Source: ISO 2768-1:1989, Table 3.
A 90° corner whose shorter side is 40 mm long may therefore deviate by ±0°30′ in class m. A 0°30′ error over 40 mm corresponds to about 0.35 mm at the end of the leg, which is wider than the ±0.3 mm linear tolerance for the same length.
What do the classes H, K and L in ISO 2768-2 mean?
ISO 2768-2 gave general geometrical tolerances in three classes, H (tightest), K and L. A drawing combined them with part 1, for example "ISO 2768-mK".
Table 4. General tolerances for straightness and flatness, ISO 2768-2, mm
| Nominal length | 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 |
Source: ISO 2768-2:1989, Table 1 (withdrawn 2021).
Table 5. General tolerances for perpendicularity, ISO 2768-2, by length of the shorter side in mm
| Shorter side | H | K | L |
|---|---|---|---|
| up to 100 | 0.2 | 0.4 | 0.6 |
| over 100 to 300 | 0.3 | 0.6 | 1 |
| over 300 to 1000 | 0.4 | 0.8 | 1.5 |
| over 1000 to 3000 | 0.5 | 1 | 2 |
Source: ISO 2768-2:1989, Table 2 (withdrawn 2021).
The same part sets a general circular run-out of 0.1 mm for H, 0.2 mm for K and 0.5 mm for L, and a general symmetry tolerance of 0.5 mm in class H over all lengths up to 3000 mm.
Is ISO 2768-2 still valid?
No. ISO withdrew ISO 2768-2:1989 on 2021-02-04, the date ISO 22081:2021 was published, and its catalogue lists ISO 22081:2021 as the replacement. In Germany, DIN ISO 2768-2:1991-04 is withdrawn and replaced by DIN EN ISO 22081:2022-10. Status as of 2026-10-30.
ISO 22081 is not a new edition with the same tables. It defines how a general geometrical specification and a general size specification are written on a drawing, using the GPS rules, and it does not contain the H, K and L values. In a note on its 2021 draft of DIN EN ISO 22081, DIN states that the replacement of ISO 2768-2 was never intended, and that undated references to ISO 2768-2 now pass to ISO 22081, which can create contractual risk on existing drawings. DIN's suggested fix is to date the reference. DIN is preparing tabulated values for use with ISO 22081 in the draft E DIN 2769:2026-09.
ISO 2768-1:1989 is unaffected. It is still published, ISO last reviewed it in 2022 and lists a revised single-part ISO 2768 in preparation. DIN ISO 2768-1:1991-06, the identical German adoption, is current.
How do you specify ISO 2768 on a drawing?
Write the standard and class in or near the title block, for example "General tolerances ISO 2768-m" or, with part 2, "ISO 2768-mK". One class applies to the whole drawing. A feature that needs a different limit gets an individual tolerance.
Check three things before a drawing goes out for quotation:
- The class is stated. Without it, untoleranced dimensions have no agreed limit.
- A reference to part 2 carries the year 1989, for the reason above.
- Dimensions under 0.5 mm carry their own tolerance, because Table 1 does not cover them.
Our network works to ISO 2768-m as standard on CNC milling and other machined parts, and tighter where the drawing specifies it. The technical drawing checklist lists the other title block entries a supplier needs.
When is a general tolerance not enough?
General tolerances suit features whose size has no functional effect within the class limits. A bearing seat, a sealing face, a locating bore or a press fit needs an individual tolerance or an ISO 286 fit such as H7/g6: for a 25 mm bore, H7 allows 0 to +0.021 mm, far tighter than the ±0.2 mm of class m. See ISO 286 fits and IT grades for those values, and the CNC machining tolerances handbook for how general tolerances, fits and GD&T combine on one part.
Frequently asked questions
- What does ISO 2768-m mean?
- The drawing applies the medium class of ISO 2768-1 to every linear and angular dimension that has no individual tolerance. A 50 mm dimension, for example, may then deviate by ±0.3 mm.
- What is the tolerance for 100 mm in ISO 2768-m?
- 100 mm falls in the range over 30 up to 120 mm, so the permissible deviation in class m is ±0.3 mm. In class f it is ±0.15 mm, in class c ±0.8 mm.
- What does ISO 2768-mK mean?
- It combines class m of ISO 2768-1 for linear and angular dimensions with class K of ISO 2768-2 for straightness, flatness, perpendicularity, symmetry and run-out of features without an individual geometrical tolerance.
- Has ISO 2768 been withdrawn?
- Only part 2. ISO 2768-2:1989 was withdrawn in February 2021, and ISO lists ISO 22081:2021 as its replacement. ISO 2768-1:1989 is still published, and a revision is in preparation.
- Does ISO 2768 apply to dimensions below 0.5 mm?
- No. ISO 2768-1 starts at 0.5 mm. For smaller nominal sizes the deviation has to be written next to the dimension itself.
Sources
- ISO 2768-1:1989, General tolerances, Part 1 (ISO catalogue)
- ISO 2768-2:1989, General tolerances, Part 2 (ISO catalogue)
- ISO 22081:2021, General geometrical specifications and general size specifications (ISO catalogue)
- ISO 2768-2:1989 life cycle, stage 95.99 dated 2021-02-04 (ISS, national ISO member)
- ISO 286-1:2010 standard tolerance grades, IT7 for 18–30 mm (table reproduced on Wikipedia)
- DIN ISO 2768-1:1991-06 (DIN Media)
- DIN ISO 2768-2:1991-04, withdrawn (DIN Media)
- E DIN EN ISO 22081:2021-12, note on the replacement of ISO 2768-2 (DIN Media)
- E DIN 2769:2026-09, tabulated values for general tolerances (DIN Media)
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