ISO 2768 general tolerances: table and calculator
ISO 2768-1 sets the permissible deviations for dimensions that have no tolerance written on the drawing. Enter a dimension and a class: the calculator gives the min and max straight away.
ISO 2768 calculator
Tolerance
±0.3
Min
49.7
Max
50.3
Range: over 30 to 120
Linear dimensions (mm)
| Range | f | m | c | v |
|---|---|---|---|---|
| 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 1,000 | ±0.3 | ±0.8 | ±2 | ±4 |
| over 1,000 to 2,000 | ±0.5 | ±1.2 | ±3 | ±6 |
| over 2,000 to 4,000 | — | ±2 | ±4 | ±8 |
Radii and chamfers (mm)
| Range | 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 |
Angles, by shorter side (mm)
| Range | 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′ |
How to read “ISO 2768-mK” in a title block
The lower-case letter is the dimensional tolerance class (ISO 2768-1): it applies to lengths, diameters, radii, chamfers and angles. The capital letter (H, K or L) is the geometrical tolerance class (ISO 2768-2): flatness, straightness, perpendicularity, symmetry, run-out. It plays no part in the min and max of a dimension.
The four tolerance classes
- f — fine: precision engineering, small parts.
- m — medium: the most common class in machining (turning, milling).
- c — coarse: welded assemblies, sheet metal, non-critical parts.
- v — very coarse: raw parts, castings, heavy fabrication.
Worked example
A 50 mm dimension with no tolerance, on a drawing marked “ISO 2768-m”: 50 mm falls in the over 30 to 120 mm range, where class m allows ±0.3 mm. The dimension must therefore be between 49.7 and 50.3 mm.
What general tolerances do not cover
- Dimensions carrying their own tolerance (for example 12.7 ±0.15).
- ISO 286 fits (Ø20 H7, Ø25 h6): their limits come from the fit tables.
- Theoretically exact (boxed) dimensions.
- Reference dimensions, shown in brackets.
Frequently asked questions
- What tolerance applies below 0.5 mm?
- ISO 2768-1 does not cover nominal sizes below 0.5 mm. The drawing must then state an explicit tolerance.
- What is the difference between ISO 2768 and DIN 7168?
- DIN 7168 is the former German general tolerance standard. Its values are close to ISO 2768, which replaced it. It still appears on older drawings: Bulleur PARFAIT supports both.
- Do general tolerances apply to angles?
- Yes. The angular deviation depends on the length of the shorter side and on the class, for example ±0° 30′ in class m for a side of 10 to 50 mm.