ISO 2768-1 General Tolerances Table (f, m, c, v)
ISO 2768-1 supplies the default tolerance for every dimension on a drawing that has no tolerance written next to it. This table lets you look up the exact deviation for a size and class in seconds, and export it for a supplier pack or shop-floor binder.
| Feature | Tolerance class | Nominal size range (mm) | Permitted deviation (mm) |
|---|---|---|---|
Linear dimension | f (fine) | 0.5 up to 3 | +/-0.05 |
Linear dimension | f (fine) | over 3 up to 6 | +/-0.05 |
Linear dimension | f (fine) | over 6 up to 30 | +/-0.1 |
Linear dimension | f (fine) | over 30 up to 120 | +/-0.15 |
Linear dimension | f (fine) | over 120 up to 400 | +/-0.2 |
Linear dimension | f (fine) | over 400 up to 1000 | +/-0.3 |
Linear dimension | f (fine) | over 1000 up to 2000 | +/-0.5 |
Linear dimension | m (medium) | 0.5 up to 3 | +/-0.1 |
Linear dimension | m (medium) | over 3 up to 6 | +/-0.1 |
Linear dimension | m (medium) | over 6 up to 30 | +/-0.2 |
Linear dimension | m (medium) | over 30 up to 120 | +/-0.3 |
Linear dimension | m (medium) | over 120 up to 400 | +/-0.5 |
Linear dimension | m (medium) | over 400 up to 1000 | +/-0.8 |
Linear dimension | m (medium) | over 1000 up to 2000 | +/-1.2 |
Linear dimension | m (medium) | over 2000 up to 4000 | +/-2 |
Linear dimension | c (coarse) | 0.5 up to 3 | +/-0.2 |
Linear dimension | c (coarse) | over 3 up to 6 | +/-0.3 |
Linear dimension | c (coarse) | over 6 up to 30 | +/-0.5 |
Linear dimension | c (coarse) | over 30 up to 120 | +/-0.8 |
Linear dimension | c (coarse) | over 120 up to 400 | +/-1.2 |
Linear dimension | c (coarse) | over 400 up to 1000 | +/-2 |
Linear dimension | c (coarse) | over 1000 up to 2000 | +/-3 |
Linear dimension | c (coarse) | over 2000 up to 4000 | +/-4 |
Linear dimension | v (very coarse) | over 3 up to 6 | +/-0.5 |
Linear dimension | v (very coarse) | over 6 up to 30 | +/-1 |
Linear dimension | v (very coarse) | over 30 up to 120 | +/-1.5 |
Linear dimension | v (very coarse) | over 120 up to 400 | +/-2.5 |
Linear dimension | v (very coarse) | over 400 up to 1000 | +/-4 |
Linear dimension | v (very coarse) | over 1000 up to 2000 | +/-6 |
Linear dimension | v (very coarse) | over 2000 up to 4000 | +/-8 |
External radius / chamfer height | f and m | 0.5 up to 3 | +/-0.2 |
External radius / chamfer height | f and m | over 3 up to 6 | +/-0.5 |
External radius / chamfer height | f and m | over 6 | +/-1 |
External radius / chamfer height | c and v | 0.5 up to 3 | +/-0.4 |
External radius / chamfer height | c and v | over 3 up to 6 | +/-1 |
External radius / chamfer height | c and v | over 6 | +/-2 |
Values are the permitted deviations from the nominal size for dimensions with no individual tolerance, per ISO 2768-1. Always confirm against the current edition of the standard before putting a value on a controlled drawing.
Default tolerance lookup inside your ERP
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How to use the table
Find the tolerance class named in the drawing note, for example ISO 2768-mK, where the first letter is the linear class and the second letter is the geometrical class. Filter by feature, then find the row whose nominal size range contains your dimension. The permitted deviation is symmetric around the nominal, so a 45 mm dimension under class m is acceptable between 44.7 and 45.3 mm. Dimensions are judged on the size band they fall in, not on the part overall length.
- Type the class (for example m) in the search box to isolate one block
- Use the radius and chamfer rows only for external edges
- Export to Excel to build an inspection plan from the default dimensions
What the standard does and does not cover
ISO 2768-1 applies to dimensions of parts produced by metal removal or formed from sheet. It covers linear sizes, external radii, chamfer heights and angular sizes. It does not override any tolerance written on the drawing, and it does not apply to dimensions in brackets, theoretical exact dimensions in a frame, or auxiliary dimensions. Geometrical defaults such as flatness and perpendicularity come from part 2 of the standard, not this table.
Choosing a class
Class m is the usual default for ordinary machining on a general purpose CNC. Class f suits parts where the machine and process are known to hold tighter limits at no extra cost. Classes c and v are for castings, weldments and rough fabrication. A general tolerance should reflect what the normal workshop accuracy delivers, so picking a class tighter than the process leads to rejects, and picking a looser class than function needs leads to assembly problems.
Common mistakes
The most frequent error is quoting the standard without a class, which leaves the note incomplete. Another is assuming the table applies to cast, forged or molded features, which have their own standards. Designers also forget that general tolerances do not apply to mating features that need a defined fit, which should carry an explicit ISO 286 tolerance. Finally, check that the title block names the right edition and that purchasing passes the note to suppliers.
- Write the full note, for example ISO 2768-mK
- Specify fits and datum-controlled features explicitly
- Check that your ERP item revision carries the drawing note
Frequently Asked Questions
What does ISO 2768-mK mean?
It means linear and angular dimensions without an individual tolerance follow class m (medium) from part 1, and geometrical features without a tolerance follow class K from part 2. The letters are chosen independently, so you may see fH, mH, cL and other combinations on drawings.
Is ISO 2768 the same as DIN 7168?
DIN 7168 was the earlier German general tolerance standard and ISO 2768 replaced it in most use. The class letters are similar, but you should not assume identical values. Use the standard cited on your drawing and confirm the edition with the customer.
Do general tolerances apply to threads and fits?
No. Threads follow their own thread standard and mating features need explicit limits, normally from ISO 286. General tolerances only cover features that would otherwise be left without any tolerance, and they must never be used to control a functional fit.
Which class does a CNC job shop usually hold?
Most CNC shops quote to class m as standard and can often hold class f on stable materials. Actual capability depends on the machine, tooling, fixturing and part size, so confirm against measured process capability rather than assuming the class is free.
If drawing notes and revision data live in your ERP or PLM, Netray can wire up a private assistant that lets planners and buyers ask what default tolerance applies to any part without opening the drawing.
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