ISO 2768 Tolerance Chart: General Tolerances for Machined Parts
ISO 2768-1 linear and angular tolerances plus ISO 2768-2 geometric tolerances in one reference. Use the lookup tool at the top for a quick ± result, or scroll to the tables to read every class by nominal size range.
Tolerance Lookup Tool
Enter a nominal dimension in millimeters, select the tolerance type, and pick the applicable ISO 2768 class. The tool returns the permissible deviation instantly—scroll down to compare against the full reference tables.
ISO 2768-1 Linear Tolerances
These are the allowed deviations for linear dimensions—length, width, height, steps, and diameters—when no individual tolerance is shown on the drawing. All values are in millimeters.
| Nominal range (mm) | f — Fine | m — Medium | c — Coarse | v — Very coarse |
|---|---|---|---|---|
| 0.5 – 3 | ±0.05 | ±0.1 | ±0.2 | — |
| Over 3 – 6 | ±0.05 | ±0.1 | ±0.3 | ±0.5 |
| Over 6 – 30 | ±0.1 | ±0.2 | ±0.5 | ±1 |
| Over 30 – 120 | ±0.1 | ±0.3 | ±0.8 | ±1.5 |
| Over 120 – 400 | ±0.2 | ±0.5 | ±1.2 | ±2.5 |
| Over 400 – 1,000 | ±0.3 | ±0.8 | ±2 | ±4 |
| Over 1,000 – 2,000 | ±0.5 | ±1.2 | ±3 | ±6 |
| Over 2,000 – 4,000 | — | ±2 | ±4 | ±8 |
ISO 2768-1 Radii & Chamfer Heights
These are the allowed deviations for broken edges: external radii and chamfer heights. Values are in millimeters by nominal edge size.
| Nominal range (mm) | f — Fine | m — Medium | c — Coarse | v — Very coarse |
|---|---|---|---|---|
| 0.5 – 3 | ±0.2 | ±0.2 | ±0.4 | ±0.4 |
| Over 3 – 6 | ±0.5 | ±0.5 | ±1 | ±1 |
| Over 6 | ±1 | ±1 | ±2 | ±2 |
ISO 2768-1 Angular Tolerances
These are the allowed deviations for angular dimensions. The shorter side of the angle sets which range to use. Values are shown in degrees and minutes of arc.
| Nominal range (mm) | f — Fine | m — Medium | c — Coarse | v — Very coarse |
|---|---|---|---|---|
| Up to 10 | ±1° | ±1° | ±1°30′ | ±3° |
| Over 10 – 50 | ±0°30′ | ±0°30′ | ±1° | ±2° |
| Over 50 – 120 | ±0°20′ | ±0°20′ | ±0°30′ | ±1° |
| Over 120 – 400 | ±0°10′ | ±0°10′ | ±0°15′ | ±0°30′ |
| Over 400 | ±0°5′ | ±0°5′ | ±0°10′ | ±0°20′ |
ISO 2768-2 Straightness & Flatness
These are the general geometric tolerances for straightness and flatness per ISO 2768-2. Values are in millimeters by the nominal length of the feature.
| Nominal range (mm) | H | K | L |
|---|---|---|---|
| Up to 10 | 0.02 | 0.05 | 0.1 |
| Over 10 – 30 | 0.05 | 0.1 | 0.2 |
| Over 30 – 100 | 0.1 | 0.2 | 0.4 |
| Over 100 – 300 | 0.2 | 0.4 | 0.8 |
| Over 300 – 1,000 | 0.3 | 0.6 | 1.2 |
| Over 1,000 – 3,000 | 0.5 | 1 | 2 |
ISO 2768-2 Perpendicularity
These are the general geometric tolerances for perpendicularity per ISO 2768-2. Values are in millimeters by the nominal length of the shorter side.
| Nominal range (mm) | H | K | L |
|---|---|---|---|
| Up to 100 | 0.2 | 0.4 | 0.6 |
| Over 100 – 300 | 0.3 | 0.6 | 1 |
| Over 300 – 1,000 | 0.4 | 0.8 | 1.5 |
| Over 1,000 – 3,000 | 0.5 | 1 | 2 |
ISO 2768-2 Symmetry
These are the general geometric tolerances for symmetry per ISO 2768-2. Values are in millimeters by the nominal length of the shorter side.
| Nominal range (mm) | H | K | L |
|---|---|---|---|
| Up to 100 | 0.5 | 0.6 | 0.6 |
| Over 100 – 300 | 0.5 | 0.6 | 1 |
| Over 300 – 1,000 | 0.5 | 0.8 | 1.5 |
| Over 1,000 – 3,000 | 0.5 | 1 | 2 |
Quick answer: what is ISO 2768?
ISO 2768 is the international default for general tolerances on machined and formed parts. When a drawing omits a tolerance on a length, angle, edge break, or basic geometric feature, ISO 2768 tells the shop how much variation is still acceptable.
The standard splits into two parts: ISO 2768-1 covers linear, angular, and broken-edge limits in classes f, m, c, and v. ISO 2768-2 covers straightness, flatness, perpendicularity, and symmetry in classes H, K, and L.
The drawing note ISO 2768-mK — medium linear plus K geometric — is the tolerance block PREMSA sees most often on CNC part prints from European and global OEMs.
Class m (medium) at a glance: 0.5–3 mm → ±0.1 mm | 6–30 mm → ±0.2 mm | 30–120 mm → ±0.3 mm | 120–400 mm → ±0.5 mm
Complete ISO 2768 guide
ISO 2768 general tolerances for CNC drawings
General tolerances save drafting time and give CNC shops a shared baseline. Instead of dimensioning every bracket hole and wall thickness to ±0.1 mm, you add one title-block note — typically ISO 2768-mK — and every undimensioned feature inherits a defined limit.
PREMSA machines aluminum, steel, and stainless components daily in Monterrey where ISO 2768 is the default on many import drawings. The lookup tool and six reference tables on this page mirror the published ISO 2768-1 and ISO 2768-2 values so engineers can verify a limit before quoting or programming CAM.
General tolerances never replace feature-specific controls. A press-fit bore still needs its own diameter and tolerance. A mating face still needs flatness or GD&T if function depends on it. ISO 2768 fills the gaps — not the critical ones.
ISO 2768-1: linear, angular, and edge classes (f / m / c / v)
ISO 2768-1 assigns a ± band to each nominal size range. Pick the range that contains your dimension, read the value for your class, and that is the total permissible deviation unless the drawing says otherwise.
- Class f (fine) — Precision work — bearing seats, dowel fits, and assemblies where small stack-up errors matter. Tighter bands mean slower feeds, more passes, and tighter inspection.
- Class m (medium) — The practical CNC default. Brackets, housings, linkages, and general mechanical parts that must assemble cleanly without premium machining cost.
- Class c (coarse) — Non-critical geometry — covers, guards, spacers, and low-load brackets where ±0.5 mm on a 120 mm wall is acceptable.
- Class v (very coarse) — Rough stock, castings, flame-cut blanks, or pre-machined forgings. Rarely stamped on finished CNC parts unless the drawing explicitly allows it.
ISO 2768-2: geometric tolerances (H / K / L)
Linear ± values control size. Geometric classes control form and orientation — how straight a shaft is, how flat a mounting face is, or how square a flange sits relative to its bore.
Class H is the tightest geometric band, K is medium, and L is coarse. A title-block note ISO 2768-mK pairs medium linear (2768-1) with medium geometric (2768-2). If only 2768-1 appears on the print, geometric defaults may not be defined — confirm with the designer before quoting.
- Straightness & flatness — Limits bow and waviness on shafts, plates, and sealing faces. Critical when a part bolts to a flat surface or slides in a bore.
- Perpendicularity — Controls how square a face is to a datum. Important for bolt circles, flange interfaces, and parts that stack in assembly.
- Symmetry — Keeps opposing features balanced about a center plane — common on symmetric brackets and linkage arms.
How to read the tolerance chart and lookup tool
Start with the nominal size — the value on the drawing before tolerance, not the measured result. Match it to the correct size range in the linear, angular, edge, or geometric table.
The lookup above automates that match: enter nominal size in mm, choose tolerance type (linear, angular, edge break, or geometric), pick your class, and get the ± limit instantly. Cross-check against the printed tables when auditing a supplier drawing or writing a quality plan.
A dash (—) in any table cell means that class is not defined for that nominal range. Do not interpolate — pick a different class or add an explicit tolerance on the drawing.
ISO 2768 vs explicit tolerances and GD&T
Explicit dimensions always win. If a hole is called 10.0 ±0.05 mm, that limit applies — not the ISO 2768-m band for a 6–30 mm feature. The same rule applies to GD&T frames: a flatness symbol with a numeric tolerance overrides the general geometric class.
Use ISO 2768 when undimensioned features are truly non-critical. Use explicit tolerances or GD&T when fit, seal, or alignment drives function. Mixing both on one drawing is normal — the title-block note handles everything else.
For tighter production limits than class m, see PREMSA's CNC tolerances guide or request a quote with STEP and drawing so the shop can confirm manufacturability before cutting metal.
Popular ISO 2768 lookups
Quick answers to the tolerance questions engineers search most often. Values assume class m (medium) linear unless noted.
- What is the ISO 2768 tolerance for 25 mm?
- For a 25 mm nominal linear dimension in class m, the permissible deviation is ±0.2 mm (range 6–30 mm). Actual limits: 24.8 mm to 25.2 mm.
- What does ISO 2768-mK mean?
- m = medium linear class (ISO 2768-1). K = medium geometric class (ISO 2768-2). Together they form the most common general-tolerance block on CNC drawings.
- ISO 2768-1 vs ISO 2768-2 — what's the difference?
- 2768-1 covers linear ±, angular, and broken-edge limits in classes f/m/c/v. 2768-2 covers straightness, flatness, perpendicularity, and symmetry in classes H/K/L.
- Which ISO 2768 class for CNC parts?
- Class m (medium) fits most machined brackets, housings, and linkages. Use f for precision fits, c for non-critical covers, v only on rough or pre-machined stock.
- ISO 2768 tolerance for 10 mm?
- Class m linear: ±0.2 mm (nominal 10 mm falls in the 6–30 mm range). Acceptable limits: 9.8 mm to 10.2 mm.
- What does a dash (—) mean in ISO 2768 tables?
- That tolerance class is not defined for that nominal size range. Choose another class or add an explicit tolerance on the drawing.
- Does ISO 2768 override GD&T?
- No. Feature control frames and explicit ± dimensions always take priority. ISO 2768 applies only where no individual tolerance is shown.
- ISO 2768 angular tolerance class m?
- Depends on the shorter side of the angle: up to 10 mm → ±1°; 10–50 mm → ±0°30′; 50–120 mm → ±0°20′; 120–400 mm → ±0°10′; over 400 mm → ±0°5′ (ISO 2768-1 Table 3).
- ISO 2768 vs ISO 286 — same thing?
- No. ISO 2768 sets general ± defaults for undimensioned features. ISO 286 defines fit systems (H7/g6, etc.) for mated shafts and bores with explicit clearance or interference.
- Can I use ISO 2768 on inch drawings?
- The standard is metric. Convert inch dimensions to mm for lookup, or specify general tolerances per ASME Y14.5 / ISO 2768-mK in the title block and dimension in mm on CNC prints sent to metric shops.
How to use this ISO 2768 tolerance chart
- PREMSA publishes this ISO 2768 tolerance chart with a live lookup tool and six reference tables covering linear, angular, broken-edge, and geometric limits from ISO 2768-1 and ISO 2768-2.
- For a 25 mm nominal dimension in class m (medium), ISO 2768-1 permits ±0.2 mm — acceptable range 24.8 mm to 25.2 mm. This is one of the most common lookup queries on machined-part drawings.
- ISO 2768-mK is the default title-block note PREMSA receives on European and global OEM CNC prints: medium linear (2768-1) plus medium geometric (2768-2).
- A dash (—) in any table cell means that tolerance class does not apply to that nominal size range; engineers must pick another class or add an explicit tolerance.
- General tolerances apply only to undimensioned features. Explicit ± dimensions, fit callouts (ISO 286), and GD&T frames always override ISO 2768 limits.
- For production CNC quoting in Monterrey, PREMSA requests STEP plus drawing with tolerance notes confirmed — request a quote or read the CNC tolerances guide.
Related Resources
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CNC Machining Tolerances Guide
How to specify standard, tight, and precision tolerances on machined parts.
View resource - Guide
CNC Design Guide for Machining
DFM rules for tolerances, holes, threads, and manufacturability on CNC parts.
Read guide - Chart
Drill Bit Size Chart
Number, letter, and fractional drill diameters in mm and inches.
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ISO 2768 tolerance chart questions
- What is ISO 2768 and when should I use it?
- ISO 2768 defines general tolerances for machined and formed parts when a drawing does not call out a specific tolerance on every dimension. It saves drafting time and gives shops a clear default for lengths, angles, radii, and basic geometry.
- What is the difference between ISO 2768-1 and ISO 2768-2?
- ISO 2768-1 sets permissible deviations for linear and angular dimensions in classes f, m, c, and v. ISO 2768-2 sets geometric tolerances—straightness, flatness, perpendicularity, symmetry—in classes H, K, and L.
- What does ISO 2768-mK mean on a drawing?
- The lowercase letter is the linear class from ISO 2768-1 (m = medium). The uppercase letter is the geometric class from ISO 2768-2 (K = medium). ISO 2768-mK is the most common general-tolerance block for CNC machined components.
- Which ISO 2768 class should I pick for CNC parts?
- For most CNC machined parts, class m (medium) is a practical default. Use f (fine) for tighter mating features, c (coarse) for non-critical covers and brackets, and v (very coarse) only for rough or pre-machined workpieces.
- How do I find the linear tolerance for a 25 mm dimension?
- Find the row where 25 mm falls (over 6 – 30), then read the column for your class. For class m, the linear tolerance is ±0.2 mm. You can also use the Tolerance Lookup Tool on this page.
- Do ISO 2768 tolerances replace GD&T on a drawing?
- No. ISO 2768 applies only where no individual tolerance is shown. Explicit GD&T frames, fit tolerances, or dimension-specific limits always take precedence over general tolerances.
ISO 2768 defines general tolerances for machined and formed parts when a drawing does not call out a specific tolerance on every dimension. It saves drafting time and gives shops a clear default for lengths, angles, radii, and basic geometry.
ISO 2768-1 sets permissible deviations for linear and angular dimensions in classes f, m, c, and v. ISO 2768-2 sets geometric tolerances—straightness, flatness, perpendicularity, symmetry—in classes H, K, and L.
The lowercase letter is the linear class from ISO 2768-1 (m = medium). The uppercase letter is the geometric class from ISO 2768-2 (K = medium). ISO 2768-mK is the most common general-tolerance block for CNC machined components.
For most CNC machined parts, class m (medium) is a practical default. Use f (fine) for tighter mating features, c (coarse) for non-critical covers and brackets, and v (very coarse) only for rough or pre-machined workpieces.
Find the row where 25 mm falls (over 6 – 30), then read the column for your class. For class m, the linear tolerance is ±0.2 mm. You can also use the Tolerance Lookup Tool on this page.
No. ISO 2768 applies only where no individual tolerance is shown. Explicit GD&T frames, fit tolerances, or dimension-specific limits always take precedence over general tolerances.
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