Tolerance chart
ISO 2768 general tolerances: chart and calculator for m, mK, f, c, v
ISO 2768 sets the general tolerances: the tolerance that applies to every dimension on a drawing that has none of its own. On a turned or milled part that is most of the dimensions. Here is what »ISO 2768-m« and »ISO 2768-mK« in the title block mean, a lookup for one dimension, and every table of both parts.
ISO 2768 calculator: limits for one dimension
–
Dimensions with a fit such as »Ø20 H7« are not covered by ISO 2768 but by ISO 286: see the ISO 286 tolerance charts.
What the title block note means
If the title block says ISO 2768-mK or ISO 2768-m, a general tolerance applies to every dimension without a tolerance of its own. The first letter is the class of part 1, the second the class of part 2:
- ISO 2768-1 – linear and angular dimensions, classes f (fine), m (medium), c (coarse) and v (very coarse), with tables for lengths, for radii and chamfer heights, and for angles.
- ISO 2768-2 – geometric tolerances without an individual frame, classes H, K and L: straightness and flatness, perpendicularity, symmetry and run-out.
So »ISO 2768-mK« means medium for sizes and K for geometry. Skip it, and you are measuring against nothing – a dimension treated as »free« in the inspection report is a classic reason for a rejected first article.
How to read the tables
Ranges run »over A up to and including B«. The first range for lengths, radii and chamfers starts at 0.5 mm inclusive; below that the standard sets no general tolerance and the tolerance has to be on the dimension itself. Two examples in class m:
- Ø12 is in the range over 6 to 30 mm: ±0.2 mm, so the limits are 11.8 and 12.2.
- 100 is in the range over 30 to 120 mm: ±0.3 mm, so 99.7 and 100.3.
Exactly 30 mm still belongs to »over 6 to 30« – the kind of edge case that makes looking it up by hand error-prone.
ISO 2768-1: linear dimensions
Permissible deviations in mm for linear dimensions without a tolerance, including diameters and distances. »–« means: not specified for this class.
| Nominal size (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 |
| 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 |
ISO 2768-1: radii and chamfer heights
Permissible deviations in mm for external radii and chamfer heights.
| Nominal size (mm) | f | m | c | v |
|---|---|---|---|---|
| 0.5 to 3 | ±0.2 | ±0.2 | ±0.4 | ±0.4 |
| over 3 to 6 | ±0.5 | ±0.5 | ±1 | ±1 |
| over 6 | ±1 | ±1 | ±2 | ±2 |
ISO 2768-1: angular dimensions
Permissible deviations by the length of the shorter leg in mm.
| Shorter leg (mm) | f | m | c | v |
|---|---|---|---|---|
| up to 10 | ±1° | ±1° | ±1°30′ | ±3° |
| over 10 to 50 | ±0°30′ | ±0°30′ | ±1° | ±2° |
| over 50 to 120 | ±0°20′ | ±0°20′ | ±0°30′ | ±1° |
| over 120 to 400 | ±0°10′ | ±0°10′ | ±0°15′ | ±0°30′ |
| over 400 | ±0°05′ | ±0°05′ | ±0°10′ | ±0°20′ |
ISO 2768-2: straightness and flatness
General tolerances in mm by nominal length.
| Nominal length (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 |
ISO 2768-2: perpendicularity
General tolerances in mm by the length of the shorter side.
| Shorter side (mm) | 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 |
ISO 2768-2: symmetry
General tolerances in mm by nominal length.
| Nominal length (mm) | H | K | L |
|---|---|---|---|
| up to 100 | 0.5 | 0.6 | 0.6 |
| over 100 to 300 | 0.5 | 0.6 | 1 |
| over 300 to 1000 | 0.5 | 0.8 | 1.5 |
| over 1000 to 3000 | 0.5 | 1 | 2 |
ISO 2768-2: run-out
General tolerance for circular radial and axial run-out in mm, independent of size.
| H | K | L |
|---|---|---|
| 0.1 | 0.2 | 0.5 |
Three things worth knowing
- Circularity is not tabulated: it equals the diameter tolerance, but is never more than the run-out tolerance.
- Exceeding a general tolerance is not automatically scrap. ISO 2768-1, section 6, says it does not lead to automatic rejection if the function of the part is not impaired. In the inspection report the characteristic is still out of tolerance; the customer decides about use, for example with a deviation permit.
- Part 2 has a successor. ISO 2768-2:1989 is listed as withdrawn; new drawings state general geometric tolerances to ISO 22081. Drawings saying »2768-mK« will stay in circulation for years and are inspected against the tables above.
The symbols of geometric tolerances are explained in GD&T symbols.