General tolerances per ISO 2768

Q: What does the callout ISO 2768-mK mean?

The first letter m gives the tolerance class for linear and angular dimensions per part 1, the second letter K the class for form and position per part 2. ISO 2768-mK is the most common combination in practice for machined parts.

Q: Which class is the usual default?

For linear dimensions m (medium) is the normal workshop accuracy, for form and position class K. Finer requirements lead to f or H, coarser processes to c/v or L. The calculator defaults to m and K.

Q: How do I read angular tolerances correctly?

The angular tolerance does not depend on the angle value but on the length of the shorter leg. A 45° and a 90° angle with an equally long short leg receive the same tolerance. Classes f and m share the same values here.

Q: What applies to dimensions below 0.5 mm?

For nominal sizes below 0.5 mm no general tolerance is specified. In that case the limit deviation must be given directly at the dimension on the drawing. The calculator flags such inputs explicitly.

Q: Does exceeding the general tolerance automatically reject the part?

No. Under the rule of both parts of the standard, exceeding a general tolerance does not necessarily reject the part as long as the function is not impaired. The assessment remains an engineering decision in the given context.

Quickly look up limit deviations for dimensions without an individual tolerance: linear, edge and angular dimensions in classes f/m/c/v (part 1) and form/position tolerances in H/K/L (part 2). All classes compared directly, plus an actual-size check with a pass/fail indicator, live with every input.

Standards situation: ISO 2768, ISO 22081 and DIN 2769Part 1 (linear and angular dimensions) remains valid. Part 2 (form and position) was replaced by DIN EN ISO 22081 in 2021; the part 2 values shown here correspond to the 1989 edition.Show details

Part 1 (linear and angular dimensions) remains valid in Germany as DIN ISO 2768-1:1991-06. The ongoing international revision (single-part ISO 2768) was in final balloting in June 2026; once published its values should be re-checked.

Part 2 (form and position) was replaced in 2021 by DIN EN ISO 22081. That standard deliberately no longer provides size-dependent tolerance values; the designer sets a general surface-profile and size tolerance, optionally based on the classes of DIN 2769:2023-04.

Legacy drawings almost always reference "ISO 2768" undated. If the old part 2 table values are to keep applying, adding the edition date on the drawing ("ISO 2768-2:1989") is recommended. The part 2 values shown here correspond to that edition.

Part 1 - linear, edge and angular dimensions

Dimension typeNominal size in mmTolerance class

Actual size in mm (optional)

Linear dimension 50 mm · Tolerance class m

Nominal size range: 30 < N ≤ 120 mm
Limit deviation: ±0.3 mm
Upper limit: 50.3 mm
Lower limit: 49.7 mm
Tolerance 2·A: 0.6 mm

All classes compared (selected class highlighted)

Class	Limit deviation	Upper limit	Lower limit
f	±0.15 mm	50.15 mm	49.85 mm
m	±0.3 mm	50.3 mm	49.7 mm
c	±0.8 mm	50.8 mm	49.2 mm
v	±1.5 mm	51.5 mm	48.5 mm

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Part 2 - form and position

FeatureReference length in mmTolerance class

Straightness / flatness · Tolerance class K

Nominal size range: 30 < N ≤ 100 mm
Permissible tolerance zone t: 0.2 mm

All classes compared (selected class highlighted)

Class	Tolerance zone t
H	0.1 mm
K	0.2 mm
L	0.4 mm

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Formulas and fundamentals

Structure of the standard

ISO 2768 collects the general tolerances that apply to every dimension on a drawing that carries no individual tolerance. Part 1 covers linear and angular dimensions in the tolerance classes f (fine), m (medium), c (coarse) and v (very coarse). Part 2 covers form and position in classes H, K and L.

Part 1: linear and angular dimensions

The part 1 values are symmetric limit deviations ±A. From the nominal size N follow:

upper limit N + A lower limit N − A tolerance 2·A

The table is accessed via the nominal size range with the lower bound exclusive and the upper bound inclusive (a < N ≤ b). For angular dimensions the access value is not the angle but the length of the shorter leg.

Part 2: form and position

Part 2 defines tolerance zones t for straightness and flatness, perpendicularity, symmetry and run-out. Perpendicularity is accessed via the shorter leg, run-out has no length reference. These values are one-sided zone widths, not ± deviations.

Boundary rules

Below 0.5 mm nominal size the general tolerance does not apply and the deviation must be stated directly at the dimension. Empty table cells (for example class f above 2000 mm or class v below 3 mm) are deliberately not specified. Above the last table range no extrapolation is done.

Worked example

Linear example: for N = 50 mm in class m the nominal size falls in the range over 30 up to 120 mm, giving a limit deviation of ±0.3 mm. This yields an upper limit of 50.3 mm and a lower limit of 49.7 mm. A measured actual size of 50.2 mm lies within the limits (pass) and uses about 67 % of the tolerance.

Frequently asked questions

What does the callout ISO 2768-mK mean?

The first letter m gives the tolerance class for linear and angular dimensions per part 1, the second letter K the class for form and position per part 2. ISO 2768-mK is the most common combination in practice for machined parts.

Which class is the usual default?

For linear dimensions m (medium) is the normal workshop accuracy, for form and position class K. Finer requirements lead to f or H, coarser processes to c/v or L. The calculator defaults to m and K.

Is ISO 2768 still valid today?

Part 1 (linear and angular dimensions) remains valid in Germany as DIN ISO 2768-1. Part 2 (form and position) was replaced in 2021 by ISO 22081, which no longer provides size-dependent table values. On legacy drawings the old part 2 values are still ubiquitous; for undated references adding the edition date is recommended.

How do I read angular tolerances correctly?

The angular tolerance does not depend on the angle value but on the length of the shorter leg. A 45° and a 90° angle with an equally long short leg receive the same tolerance. Classes f and m share the same values here.

What applies to dimensions below 0.5 mm?

For nominal sizes below 0.5 mm no general tolerance is specified. In that case the limit deviation must be given directly at the dimension on the drawing. The calculator flags such inputs explicitly.

Does exceeding the general tolerance automatically reject the part?

No. Under the rule of both parts of the standard, exceeding a general tolerance does not necessarily reject the part as long as the function is not impaired. The assessment remains an engineering decision in the given context.

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