ISO 2768 Tolerance Chart & Calculator (mK, fH, cL Classes)
When an engineering drawing specifies ISO 2768-mK, untoleranced linear dimensions follow ISO 2768-1 Class m (Medium) and untoleranced form features follow ISO 2768-2 Class K. For a 50.0 mm dimension, the linear tolerance is ±0.30 mm (49.70 to 50.30 mm), flatness is 0.20 mm, and perpendicularity is 0.40 mm.
ISO 2768-1 & ISO 2768-2 General Linear, Broken-Edge & Geometrical Tolerances Calculator (ISO 2768-2 withdrawn, superseded by ISO 22081:2021)
Decode title-block callouts such as ISO 2768-mK or ISO 2768-fH: enter your nominal dimension (0.5 to 4000 mm) and chamfer/radius size to get exact ± linear limits, broken-edge tolerances, flatness/straightness, perpendicularity, and runout.
How Do ISO 2768-1 (f, m, c, v) and ISO 2768-2 (H, K, L) Work Together?
On modern mechanical prints, adding individual ± tolerances to every non-critical bracket width, flange thickness, and chamfer clutters the drawing and increases inspection cost. Published by International Organization for Standardization (ISO) and adopted across Europe and Asia as DIN ISO 2768, the standard splits general shop tolerances into two parts: Part 1 assigns symmetric ± deviations to linear dimensions, external radii, and angular dimensions across four machining grades—f (fine), m (medium), c (coarse), and v (very coarse)—while Part 2 (ISO 2768-2:1989, withdrawn and superseded by ISO 22081:2021) assigned geometric envelope limits for straightness, flatness, perpendicularity, symmetry, and circular runout across three classes: H, K, and L.
Note a critical boundary rule enforced by ISO 2768-1: nominal step boundaries are defined as "over X up to and including Y". Thus, a 30.00 mm dimension falls inside the >6 to 30 mm column (±0.20 mm in Class m), whereas a 30.01 mm dimension steps into the >30 to 120 mm column (±0.30 mm in Class m). For cylindrical bearing fits or dowel holes that require tighter control than ISO 2768-f, designers override the general tolerance with an explicit ISO 286 H7/g6 hole and shaft fit or an ASME Y14.5 GD&T true position callout.
| Nominal Dimension Band (mm) | Class f (Fine) | Class m (Medium — Shop Std) | Class c (Coarse) | Class v (Very Coarse) |
|---|---|---|---|---|
| >0.5 to 3 mm | ±0.05 mm | ±0.10 mm | ±0.20 mm | — |
| >3 to 6 mm | ±0.05 mm | ±0.10 mm | ±0.30 mm | ±0.50 mm |
| >6 to 30 mm | ±0.10 mm | ±0.20 mm | ±0.50 mm | ±1.00 mm |
| >30 to 120 mm | ±0.15 mm | ±0.30 mm | ±0.80 mm | ±1.50 mm |
| >120 to 400 mm | ±0.20 mm | ±0.50 mm | ±1.20 mm | ±2.50 mm |
| >400 to 1000 mm | ±0.30 mm | ±0.80 mm | ±2.00 mm | ±4.00 mm |
| >1000 to 2000 mm | ±0.50 mm | ±1.20 mm | ±3.00 mm | ±6.00 mm |
| >2000 to 4000 mm | — | ±2.00 mm | ±4.00 mm | ±8.00 mm |
Broken Edges, Angular Deviations, and ISO 2768-2 Geometrical Limits
External corner radii and 45° chamfer heights (broken edges) follow a dedicated table in ISO 2768-1: from 0.5 to 3 mm, the tolerance is ±0.2 mm for classes f and m (or ±0.4 mm for c and v); from >3 to 6 mm, it is ±0.5 mm for f/m (±1.0 mm for c/v). Under ISO 2768-2, circular runout is fixed at 0.1 mm (H), 0.2 mm (K), and 0.5 mm (L) regardless of shaft diameter. Symmetry is not tabulated on this page until it is checked against the primary standard, so no symmetry band is quoted here. ISO 2768-2:1989 is withdrawn and superseded by ISO 22081:2021; the values in this section are its historical figures, kept only for drawings that still cite it.
| Nominal Feature Length | Straightness & Flatness (H / K / L) | Perpendicularity (H / K / L) | Circular Runout (H / K / L) |
|---|---|---|---|
| Up to 10 mm | 0.02 mm (H) / 0.05 mm (K) / 0.10 mm (L) | 0.20 mm (H) / 0.40 mm (K) / 0.60 mm (L) | 0.10 mm (H) / 0.20 mm (K) / 0.50 mm (L) |
| Up to 30 mm | 0.05 mm (H) / 0.10 mm (K) / 0.20 mm (L) | 0.20 mm (H) / 0.40 mm (K) / 0.60 mm (L) | 0.10 mm (H) / 0.20 mm (K) / 0.50 mm (L) |
| Up to 100 mm | 0.10 mm (H) / 0.20 mm (K) / 0.40 mm (L) | 0.20 mm (H) / 0.40 mm (K) / 0.60 mm (L) | 0.10 mm (H) / 0.20 mm (K) / 0.50 mm (L) |
| Up to 300 mm | 0.20 mm (H) / 0.40 mm (K) / 0.80 mm (L) | 0.30 mm (H) / 0.60 mm (K) / 1.00 mm (L) | 0.10 mm (H) / 0.20 mm (K) / 0.50 mm (L) |
| Up to 1000 mm | 0.30 mm (H) / 0.60 mm (K) / 1.20 mm (L) | 0.40 mm (H) / 0.80 mm (K) / 1.50 mm (L) | 0.10 mm (H) / 0.20 mm (K) / 0.50 mm (L) |
| Up to 3000 mm | 0.40 mm (H) / 0.80 mm (K) / 1.60 mm (L) | 0.50 mm (H) / 1.00 mm (K) / 2.00 mm (L) | 0.10 mm (H) / 0.20 mm (K) / 0.50 mm (L) |
Worked Examples: Inspecting Parts to ISO 2768-mK and ISO 2768-fH
Worked Example 1 (50 mm Block with 2 mm Chamfer under ISO 2768-mK): For a milled manifold block measuring 50.0 mm with a 2.0 × 45° chamfer under ISO 2768-mK, our engine returns a linear window of 49.70 to 50.30 mm (±0.30 mm), a chamfer tolerance of ±0.20 mm, a flatness zone of 0.20 mm, and a squareness tolerance of 0.40 mm.
Worked Example 2 (15 mm Precision Sensor Housing in ISO 2768-fH vs 250 mm Weldment in cL): Tightening the callout to ISO 2768-fH on a 15.0 mm feature narrows the allowed dimension to 14.90–15.10 mm (±0.10 mm) with flatness 0.05 mm and runout 0.10 mm. Conversely, a 250.0 mm plate under ISO 2768-cL allows ±1.20 mm (248.80–251.20 mm). Remember to verify gage temperature error in the machining thermal expansion calculator.
Flatness and perpendicularity symbols follow International Organization for Standardization (ISO) ISO 1101, and the untoleranced geometric zones are now governed by International Organization for Standardization (ISO) ISO 22081:2021, because ISO 2768-2 was withdrawn.
Check a finished part against the window above before accepting it: measure the linear feature with a calibrated micrometer or caliper against the allowed limits, check each broken edge with a radius or chamfer gage against the ISO 2768-1 band, and check flatness on a surface plate with a straightedge and dial indicator. Where a drawing still cites ISO 2768-2:1989, record that edition on the inspection report.
Cite this page
ToolSpecVault Engineering Data Team. (2026, November 2). ISO 2768 Tolerance Chart & Calculator (mK, fH, cL Classes). ToolSpecVault. https://toolspecvault.com/iso-2768-general-tolerances-chart-calculator/