Dimensional tolerances

ISO 2768-1 General Tolerances

Calculator and general tolerance tables for linear dimensions, radii, chamfers and angular dimensions according to ISO 2768-1. Enter a nominal dimension and select class f, m, c or v to immediately obtain the dimensional limits.

The ISO 2768-1 standard defines general tolerances for dimensions on technical drawings that do not have an individual tolerance indication. The available classes are f (fine), m (medium), c (coarse) and v (very coarse).

ISO 2768-1 Tolerance Calculator

Calculate tolerances for linear dimensions, radii and chamfers, or angular dimensions.

Dimension type
mm
You can use either a comma or a decimal point.
Tolerance class

This calculator is provided for information purposes. For design, inspection or product acceptance, always verify the drawing, the applicable edition of the referenced standard and any contractual requirements.

What is ISO 2768-1?

ISO 2768-1 defines general tolerances for linear and angular dimensions without an individual tolerance indication. Its purpose is to simplify technical drawings: instead of specifying a tolerance next to every non-critical dimension, a general tolerance class can be indicated in the title block.

The standard is mainly intended for dimensions produced by material removal and for parts formed from sheet metal. It covers linear dimensions, diameters, distances, external radii, chamfer heights and angular dimensions that fall within its scope.

Important for cast dimensions. ISO 2768-1 is not intended as a general standard for the “as-cast” dimensional tolerances of castings or investment castings. Specific standards in the ISO 8062 series apply to castings. A dimension subsequently obtained by machining may instead be controlled according to ISO 2768-1 when appropriately specified on the drawing.

When it does not apply

ISO 2768-1 does not replace a specific tolerance stated directly on a dimension. Among other cases, it does not apply to auxiliary dimensions shown in parentheses or to theoretically exact dimensions shown in a rectangular frame.

ISO 2768-1 Tolerance Classes: f, m, c, v

The selected class determines the allowable deviation range. The class should be chosen according to the manufacturing process and the functional requirements of the component, avoiding unnecessarily tight tolerances.

f

Fine

The tightest general tolerance of the four classes.

m

Medium

Intermediate class frequently used for general machining.

c

Coarse

Allows larger deviations than classes f and m.

v

Very coarse

Class with the widest dimensional deviations provided by the table.

ISO 2768-1 Table for Linear Dimensions

The deviations shown are symmetrical about the nominal dimension and are expressed in millimetres.

Nominal dimension range (mm) f — fine m — medium c — coarse v — very coarse
from 0.5 to 3±0.05±0.10±0.20—
over 3 up to 6±0.05±0.10±0.30±0.50
over 6 up to 30±0.10±0.20±0.50±1.00
over 30 up to 120±0.15±0.30±0.80±1.50
over 120 up to 400±0.20±0.50±1.20±2.50
over 400 up to 1000±0.30±0.80±2.00±4.00
over 1000 up to 2000±0.50±1.20±3.00±6.00
over 2000 up to 4000—±2.00±4.00±8.00

For nominal dimensions below 0.5 mm, the tolerance must be specified directly on the drawing. The “—” symbol indicates that no value is specified for that class and range.

100 mm
class m

Example: 100 mm dimension with ISO 2768-m

100 mm falls within the range over 30 up to 120 mm. For class m, the deviation is ±0.30 mm.

Lower limit: 99.70 mm
Upper limit: 100.30 mm

Tolerances for External Radii and Chamfer Heights

ISO 2768-1 provides a separate table for external radii and chamfer heights of broken edges.

Nominal dimension (mm) f — fine m — medium c — coarse v — very coarse
from 0.5 to 3±0.20±0.20±0.40±0.40
over 3 up to 6±0.50±0.50±1.00±1.00
over 6±1.00±1.00±2.00±2.00

Also in this case, for nominal dimensions below 0.5 mm an individual tolerance indication is required.

ISO 2768-1 Tolerances for Angular Dimensions

For an angular dimension, the tolerance is not selected according to the angle value itself, but according to the length of the shorter side forming the angle. Values are expressed in degrees and minutes.

Shorter side length (mm) f — fine m — medium c — coarse v — very coarse
up to 10±1°±1°±1°30′±3°
over 10 up to 50±0°30′±0°30′±1°±2°
over 50 up to 120±0°20′±0°20′±0°30′±1°
over 120 up to 400±0°10′±0°10′±0°15′±0°30′
over 400±0°5′±0°5′±0°10′±0°20′
Example: for a 90° angle with a shorter side of 80 mm, class m uses the “over 50 up to 120 mm” range, so the general angular deviation is ±0°20′.

How to Indicate ISO 2768-1 on a Technical Drawing

The general tolerance class is normally specified in the title block or in the general notes of the drawing. An indication such as:

ISO
2768-m

Meaning of ISO 2768-m

The letter m identifies the medium class of ISO 2768-1. The general tolerance applies to dimensions within the scope of the standard that do not have their own tolerance indication.

If a dimension is specified, for example, as 25 ±0.05, that individual tolerance takes precedence over the general tolerance.

Useful Checks Before Applying a General Tolerance

  • Check that the dimension falls within the scope of the standard.
  • Check whether an individual tolerance is already specified on the drawing.
  • Correctly identify the general tolerance class stated in the title block.
  • Assess whether functional dimensions require a tighter or different specific tolerance.
  • For mating features, check whether dedicated tolerance and fit systems are required.

Status of ISO 2768 in 2026

At the time of publication of this page, ISO 2768-1:1989 is still current. However, ISO indicates that this edition is intended to be replaced by the new ISO 2768, Edition 2, which is currently in the publication process.

The former ISO 2768-2:1989, concerning general geometrical tolerances, has been withdrawn; ISO identifies ISO 22081:2021 as its revision/replacement.

Note: this page intentionally focuses on ISO 2768-1 and dimensional tolerances. Existing drawings still frequently contain historical designations such as “ISO 2768-mK”; however, the geometrical tolerance portion must be assessed in accordance with the current standards framework.

Frequently Asked Questions About ISO 2768-1 Tolerances

What does ISO 2768-m mean?
It indicates the application of ISO 2768-1 class m (medium) to drawing dimensions that do not have an individual tolerance and fall within the scope of the standard.
What is the ISO 2768-m tolerance for a 100 mm dimension?
A 100 mm dimension falls within the range over 30 up to 120 mm. In class m, the deviation is ±0.30 mm, so the limits are 99.70 mm and 100.30 mm.
What are the ISO 2768-1 tolerance classes?
The four classes are f (fine), m (medium), c (coarse) and v (very coarse).
Does ISO 2768-1 apply to dimensions below 0.5 mm?
No. For nominal dimensions below 0.5 mm, the tolerance must be specified directly next to the relevant dimension.
Does a specific tolerance on the drawing take precedence over ISO 2768?
Yes. The general tolerance applies to dimensions without an individual tolerance indication. If a dimension has a specific tolerance, that specific indication is used.
Is ISO 2768-1 used for castings?
The standard is mainly intended for dimensions produced by material removal or sheet-metal forming. Specific standards in the ISO 8062 series apply to casting dimensional tolerances. For a machined dimension on a casting, ISO 2768-1 may be specified when appropriate.
What determines the tolerance of an angular dimension?
It depends on the length of the shorter side forming the angle. It does not depend directly on the nominal angle value.
Is ISO 2768-2 still current?
No. ISO 2768-2:1989 has been withdrawn and replaced by ISO 22081:2021 for general geometrical specifications.

Standards References

The content and calculator are provided for information purposes and do not replace purchasing or consulting the official standard applicable to the project.