General tolerances per ISO 2768
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.
Part 1 – linear, edge and angular dimensions
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 |
Part 2 – form and position
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 |
Standards situation: ISO 2768, ISO 22081 and DIN 2769
Formulas and fundamentals
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.
The part 1 values are symmetric limit deviations ±A. From the nominal size N follow the upper limit N + A, the lower limit N − A and the 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 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.
Related tools
Fit calculator ISO 286
Determine limit deviations, clearance and interference for hole and shaft per ISO 286.
Tolerance stackup Monte Carlo
Calculate tolerance stackups per DIN 7186 arithmetically, statistically and via Monte Carlo simulation.
GD&T true position per ISO 1101
Evaluate position tolerances per ISO 1101: actual deviation, true position and bonus tolerance.