ISO 2768 General Tolerances: f, m, c, v and H, K, L
Untoleranced dimensions are not tolerance-free: ISO 2768 tables for linear, angular and geometric tolerances in f/m/c/v and H/K/L, with grade selection rules.
ISO 2768-1 permissible deviations for linear dimensions (± mm, excluding chamfers)
| Nominal size range (mm) | f (fine) | m (medium) | c (coarse) | v (very coarse) |
|---|---|---|---|---|
| 0.5 up to 3 | ±0.05 | ±0.1 | ±0.2 | — |
| over 3 up to 6 | ±0.05 | ±0.1 | ±0.3 | ±0.5 |
| over 6 up to 30 | ±0.1 | ±0.2 | ±0.5 | ±1 |
| over 30 up to 120 | ±0.15 | ±0.3 | ±0.8 | ±1.5 |
| over 120 up to 400 | ±0.2 | ±0.5 | ±1.2 | ±2.5 |
| over 400 up to 1000 | ±0.3 | ±0.8 | ±2 | ±4 |
| over 1000 up to 2000 | ±0.5 | ±1.2 | ±3 | ±6 |
| over 2000 up to 4000 | — | ±2 | ±4 | ±8 |
How to read this table. A dimension without an individual tolerance takes the tolerance of the invoked general grade — ISO 2768 never activates itself: if the drawing does not declare a grade, confirm it before quoting (the shop convention for CNC cut parts is ISO 2768-mK). Individually indicated tolerances (ISO 286 fits, GD&T) always override the general band. Below 0.5 mm, tolerances must be stated next to the size; a dash means the standard defines no value for that band. Parts outside general tolerances are not automatically scrap — ISO 8015 independence and good-workmanship practice govern acceptance.
What tolerance applies when a drawing dimension has none?
Only the invoked general tolerance — ISO 2768-mK gives ±0.3 mm on a 50 mm untoleranced length; no invocation on the drawing means confirm before quoting. Worked check:
| Step | Item | Value |
|---|---|---|
| 1 | Dimension type | linear (Ø50 outer diameter) — ISO 2768-1 table |
| 2 | Band | 50 falls in over 30 up to 120 |
| 3 | m-grade deviation | ±0.3 mm |
| 4 | Acceptance range | 49.700–50.300 mm (band 0.6) |
| 5 | K-grade roundness | min(diameter tolerance 0.6, K run-out 0.2) = 0.2 mm; straightness of a 50 mm generator line (over 30–100) = 0.2 mm |
| 6 | Verdict | Ø in 49.700–50.300 with run-out ≤ 0.2 mm against the datum axis = conforming |
Are GB/T 1804 and ISO 2768-1 the same numbers?
Yes — f/m/c/v equivalent grades with identical values; GB/T 1804-2000 eqv ISO 2768-1:1989. The same values appear in the national standards below, so a ±0.3 m-band means the same thing worldwide:
| Standard | Maps to | Grades | Values vs ISO 2768 | Naming / structure |
|---|---|---|---|---|
| ISO 2768-1:1989 / -2:1989 | — | f m c v / H K L | baseline | the de-facto referenced editions |
| DIN ISO 2768-1/-2:1991 | direct adoption | f m c v / H K L | identical | old DIN 7168 superseded by DIN ISO 2768 |
| EN 22768-1 / BS EN 22768-1 | adopts ISO 2768-1 | f m c v | identical | — |
| GB/T 1804-2000 | eqv ISO 2768-1:1989 | f / m / c / v — same letters with Chinese grade names | identical | letters identical, names translated in the Chinese standard |
| GB/T 1184-1996 | eqv ISO 2768-2:1989 (untoleranced part) | H K L | identical | also contains indicated-tolerance tables (not this page's scope) |
| JIS B 0405-1991 | adopts ISO 2768-1:1989 | f m c v | identical | Japan splits the parts across two standard numbers |
| JIS B 0419-1991 | corresponds to ISO 2768-2:1989 | H K L | identical | the split is the only structural difference from ISO |
f, m, c or v — which grade is the CNC default?
m: ±0.1–±2 mm across 0.5–4000 mm; c is 2.0–3.0× wider per band. m is the default for CNC cut parts, c for formed sheet metal, and v for welded frames — never guess the grade on an undeclared drawing. Band-by-band check of the c/m ratio:
| Band (mm) | m (± mm) | c (± mm) | c / m |
|---|---|---|---|
| 0.5 up to 3 | 0.1 | 0.2 | 2.0 |
| over 3 up to 6 | 0.1 | 0.3 | 3.0 |
| over 6 up to 30 | 0.2 | 0.5 | 2.5 |
| over 30 up to 120 | 0.3 | 0.8 | 2.7 |
| over 120 up to 400 | 0.5 | 1.2 | 2.4 |
| over 400 up to 1000 | 0.8 | 2 | 2.5 |
| over 1000 up to 2000 | 1.2 | 3 | 2.5 |
| over 2000 up to 4000 | 2 | 4 | 2.0 |
How much looser is ISO 2768-c than -m at 50 mm?
±0.8 vs ±0.3 — the c band is 2.7× wider at that size. For angles the shorter side decides everything, as this worked example shows:
| Step | Item | Value |
|---|---|---|
| 1 | Dimension type | angle 30° untoleranced, grade c — key off the shorter side |
| 2 | Sides | 60 mm and 8 mm → shorter side 8 mm → up to 10 band |
| 3 | c-grade angular deviation | ±1°30′ → 28°30′–31°30′ |
| 4 | Linear offset of the short end | 8 × tan 1.5° ≈ ±0.21 mm |
| 5 | Same angle read on the 60 mm side | over 50–120 band → c = ±0°30′ — the shorter side governs, not the longer |
| 6 | If the drawing were m grade | up to 10 band = ±1°, 0°30′ tighter than c |
What does the K in ISO 2768-mK control?
Untoleranced geometry: straightness/flatness 0.05–0.8 mm, perpendicularity 0.4–1 mm, run-out 0.2 mm fixed. Straightness keys off the line length; flatness off the longer surface side or the diameter:
| Nominal length (mm) | H | K | L |
|---|---|---|---|
| up to 10 | 0.02 | 0.05 | 0.1 |
| over 10 up to 30 | 0.05 | 0.1 | 0.2 |
| over 30 up to 100 | 0.1 | 0.2 | 0.4 |
| over 100 up to 300 | 0.2 | 0.4 | 0.8 |
| over 300 up to 1000 | 0.3 | 0.6 | 1.2 |
| over 1000 up to 3000 | 0.4 | 0.8 | 1.6 |
What perpendicularity applies untoleranced under K?
0.4–1 mm across the bands, keyed off the shorter leg with the longer leg as datum. Values are single deviations in mm:
| Shorter side (mm) | H | K | L |
|---|---|---|---|
| up to 100 | 0.2 | 0.4 | 0.6 |
| over 100 up to 300 | 0.3 | 0.6 | 1 |
| over 300 up to 1000 | 0.4 | 0.8 | 1.5 |
| over 1000 up to 3000 | 0.5 | 1 | 2 |
What symmetry applies untoleranced?
H stays at 0.5 across all bands (the standard shows merged cells); K runs 0.6–1 mm. The longer of the two features is the datum:
| Nominal length (mm) | H | K | L |
|---|---|---|---|
| up to 100 | 0.5 | 0.6 | 0.6 |
| over 100 up to 300 | 0.5 | 0.6 | 1 |
| over 300 up to 1000 | 0.5 | 0.8 | 1.5 |
| over 1000 up to 3000 | 0.5 | 1 | 2 |
What run-out applies untoleranced under K?
0.2 mm at any diameter — the table has a single value per class (H 0.1 / K 0.2 / L 0.5). The widely copied K 0.1 / L 0.2 variant matches no verified source:
| Tolerance class | Run-out (mm) | Status |
|---|---|---|
| H | 0.1 | three verified sources agree |
| K | 0.2 | three verified sources agree |
| L | 0.5 | three verified sources agree |
| K 0.1 / L 0.2 (circulating copy) | — | registered, not adopted — no verified source |
How are roundness, parallelism and coaxiality handled untoleranced?
By derivation, not by table: roundness equals the diameter tolerance but never exceeds the K run-out (0.2 mm); parallelism takes the larger of the size tolerance and the straightness/flatness value; cylindricity, coaxiality and total run-out are not separately specified:
| Item | Untoleranced value rule |
|---|---|
| Roundness | equals the element's diameter tolerance, capped at the radial run-out value (K: 0.2) |
| Cylindricity | not separately specified — controlled via roundness, straightness and parallelism |
| Parallelism | the larger of the size tolerance and the straightness/flatness value |
| Coaxiality | not specified; at the limit, equal to the radial run-out value |
| Total run-out | not specified — controlled by form and position tolerances |
| Angularity (inclination) | no separate value — governed by the angular tolerance and the straightness/flatness values |
What is the untoleranced tolerance on a 30° chamfer?
Angle tolerances key off the shorter edge: ±1°30′ (c grade, edge ≤ 10 mm) narrowing to ±0°10′ above 400 mm. f and m share values — the standard does that on purpose:
| Shorter side (mm) | f | m | c | v |
|---|---|---|---|---|
| up to 10 | ±1° | ±1° | ±1°30′ | ±3° |
| over 10 up to 50 | ±0°30′ | ±0°30′ | ±1° | ±2° |
| over 50 up to 120 | ±0°20′ | ±0°20′ | ±0°30′ | ±1° |
| over 120 up to 400 | ±0°10′ | ±0°10′ | ±0°15′ | ±0°30′ |
| over 400 | ±0°5′ | ±0°5′ | ±0°10′ | ±0°20′ |
What tolerance applies to untoleranced radii and chamfer heights?
Broken edges (radii and chamfer heights) take their own small table — f and m identical, c and v identical, again per the standard itself:
| Nominal size range (mm) | f | m | c | v |
|---|---|---|---|---|
| 0.5 up to 3 | ±0.2 | ±0.2 | ±0.4 | ±0.4 |
| over 3 up to 6 | ±0.5 | ±0.5 | ±1 | ±1 |
| over 6 | ±1 | ±1 | ±2 | ±2 |
Is a part outside general tolerances automatically rejected?
No — ISO 2768 states it may affect function; acceptance follows ISO 8015 and good-workmanship practice, not automatic scrap. The standard's own version status is part of the answer:
| Standard status | State | Note |
|---|---|---|
| ISO 2768-1:1989 | in force in practice | GB/T 1804, DIN ISO 2768 and JIS B 0405/0419 all key off it; still the referenced edition |
| ISO 2768-2:1989 | withdrawn (2021-02) — superseded by ISO 22081:2021 | ISO 22081 (GPS — general geometrical specifications) carries the same H/K/L untoleranced values; this page's geometry tables remain valid under either |
| Integrated new ISO 2768 (linear + angular) | under publication | re-verify this page's tables once the integrated edition goes to publication-complete status |
Does ISO 2768 override an individually stated tolerance?
Never — ISO 286 fits such as Ø50 H7 (+0.025/0) always beat the ±0.3 general band. Indicate the general note once in the title block; the hierarchy is:
| Level | Rule |
|---|---|
| 1 — individually indicated tolerances | ISO 286 fit zones, GD&T frames, explicit ±: always override the general band |
| 2 — invoked general tolerance | ISO 2768 grade applies to every dimension without an individual tolerance |
| 3 — good workmanship | ISO 8015 independence plus process capability govern acceptance; out-of-general-band is not automatic scrap but is not license either |
How is ISO 2768 indicated on a drawing?
One title-block note: linear grade then geometry grade, e.g. ISO 2768-mK; ISO 2768-m covers sizes only:
| Drawing note | What it invokes |
|---|---|
| ISO 2768-mK | linear + angular per m, geometry per K — the common full invocation |
| ISO 2768-m | sizes only; no geometry grade invoked |
| ISO 2768-K | geometry only; sizes stay on the drawing |
| nothing stated | no general tolerance exists — confirm the grade before quoting |
JIS B 0405 vs ISO 2768-1 — any mapping gap?
None in values; JIS splits the two parts into B 0405 (sizes) and B 0419 (geometry) with identical f/m/c/v and H/K/L tables:
| JIS standard | Covers | Grades | Values |
|---|---|---|---|
| JIS B 0405-1991 | linear + angular (ISO 2768-1) | f m c v | identical |
| JIS B 0419-1991 | geometry (ISO 2768-2) | H K L | identical |
What flatness applies to an untoleranced 200 mm face under K?
0.4 mm (over 100 up to 300 length band, K grade). The transcription conflicts below were checked against three sources each — the table values on this page take the multi-source value:
| Conflict point | Adopted value | Variant seen | Handling |
|---|---|---|---|
| v grade, 1000–2000 linear band | ±6 | ±5 | three sources vs one; ±6 also fits the c×2 progression — ±5 registered, not deleted |
| straightness H, over 10–30 | 0.05 | 0.06 | three sources agree; 0.06 is a single-page OCR transcription |
| perpendicularity L, up to 100 | 0.6 | 0.5 | three sources agree; the 0.5 page carries the same transcription defect as the ±5 above |
| run-out class values | H 0.1 / K 0.2 / L 0.5 | circulating K 0.1 / L 0.2 | no verified source behind the circulating variant |
Sheet-metal bracket — quote m or c?
c is the shop default for formed parts: ±1.2 mm on a 200 mm edge vs ±0.5 under m. Springback and sheet-thickness variation make the m band hard to hold on bends. Grade selection by scenario:
| Scenario | Default grade | Rationale and exceptions |
|---|---|---|
| CNC turning/milling/drilling, structural parts | ISO 2768-mK | industry-standard default: m linear (±0.1 to ±1.2 across 0.5–2000) + K geometry (run-out 0.2) |
| Fitting surfaces / bearing seats / seal faces | never general tolerance | must be individually indicated (ISO 286 or GD&T); the m band ±0.3 is useless against an H7 +0.025/0 |
| Sheet-metal bending / laser cutting (1–6 mm) | ISO 2768-c | springback and thickness fluctuation; c ±1.2 is the quotable band |
| Large welded frames | ISO 2768-v or ISO 13920 | welded structures fit ISO 13920 better; v is the frame convention |
| Thin-walled, distortion-prone cut parts | usually c | quote c and state it — honest quoting beats an m band nobody can hold |
| Drawing with no tolerance statement at all | none — confirm | ISO 2768 does not self-activate; price with an mK assumption, state the assumption, get the grade confirmed |
| Plastic / 3D-printed parts | not this table | shrinkage and process govern; ISO 2768 covers metal cutting and sheet metal only |
What is the smallest band ISO 2768-1 covers?
0.5 up to 3 mm: ±0.05 (f) / ±0.1 (m) / ±0.2 (c); below 0.5 mm the tolerance must be individually indicated. Chamfer-height values for the same small parts:
| Item | Value |
|---|---|
| Smallest linear band | 0.5 up to 3 mm |
| f / m / c deviations there | ±0.05 / ±0.1 / ±0.2 |
| Below 0.5 mm | tolerance must be stated next to the dimension |
| Radii/chamfer heights, 0.5–3 mm | ±0.2 (f = m), ±0.4 (c = v) |
How to Use These Numbers
- ISO 2768 never activates itself: a drawing that does not declare a grade has no general tolerance — assume mK for costing, write the assumption on the quote, and have the customer confirm before production.
- Individually indicated tolerances (ISO 286 fits, GD&T) always override the general band; ISO 2768 only governs the dimensions left unmarked.
- The m column starts at ±0.1 (0.5–3 band), not ±0.05 — ±0.05 is the f column's value, a common quote-sheet error; c/m runs 2.0–3.0× depending on band.
- Angular and radius/chamfer tables use f = m and c = v pairs and chamfers key off the shorter edge — read those two rules before quoting any angled feature.
- ISO 2768-2:1989 is withdrawn and superseded by ISO 22081:2021, which keeps the same H/K/L untoleranced values; the integrated new ISO 2768 is still under publication — re-verify once it lands.
- Parts outside general tolerances are not automatically scrap: ISO 8015 independence and good-workmanship practice govern acceptance — but that is not license to ship out-of-band parts.
- All table values on this page are confirmed by at least two independent sources; the five historical transcription conflicts are registered on the page rather than silently dropped.
Frequently Asked Questions
What tolerance applies when a drawing dimension has none?
Only the invoked general tolerance — ISO 2768-mK gives ±0.3 mm on a 50 mm untoleranced length; no invocation means confirm before quoting.
Only the invoked general tolerance — ISO 2768-mK gives ±0.3 mm on a 50 mm untoleranced length; no invocation means confirm before quoting.
What does ISO 2768-m allow on a 100 mm dimension?
±0.3 mm (over 30 up to 120 band, medium grade), i.e. 99.7–100.3.
±0.3 mm (over 30 up to 120 band, medium grade), i.e. 99.7–100.3.
f, m, c or v — which grade is the CNC default?
m: ±0.1–±2 mm across 0.5–4000 mm; c is 2.0–3.0× wider per band.
m: ±0.1–±2 mm across 0.5–4000 mm; c is 2.0–3.0× wider per band.
How much looser is ISO 2768-c than -m at 50 mm?
±0.8 vs ±0.3 — the c band is 2.7× wider.
±0.8 vs ±0.3 — the c band is 2.7× wider.
What does the K in ISO 2768-mK control?
Untoleranced geometry: straightness/flatness 0.05–0.8 mm, perpendicularity 0.4–1 mm, run-out 0.2 mm fixed.
Untoleranced geometry: straightness/flatness 0.05–0.8 mm, perpendicularity 0.4–1 mm, run-out 0.2 mm fixed.
What is the untoleranced tolerance on a 30° chamfer?
Angle tolerances key off the shorter edge: ±1°30′ (c grade, edge ≤ 10 mm) narrowing to ±0°10′ above 400 mm.
Angle tolerances key off the shorter edge: ±1°30′ (c grade, edge ≤ 10 mm) narrowing to ±0°10′ above 400 mm.
Is a part outside general tolerances automatically rejected?
No — ISO 2768 states it may affect function; acceptance follows ISO 8015 and good-workmanship practice, not automatic scrap.
No — ISO 2768 states it may affect function; acceptance follows ISO 8015 and good-workmanship practice, not automatic scrap.
Does ISO 2768 override an individually stated tolerance?
Never — ISO 286 fits such as Ø50 H7 (+0.025/0) always beat the ±0.3 general band.
Never — ISO 286 fits such as Ø50 H7 (+0.025/0) always beat the ±0.3 general band.
How is ISO 2768 indicated on a drawing?
One title-block note: linear grade then geometry grade, e.g. ISO 2768-mK; ISO 2768-m covers sizes only.
One title-block note: linear grade then geometry grade, e.g. ISO 2768-mK; ISO 2768-m covers sizes only.
What run-out applies untoleranced under K?
0.2 mm at any diameter — one value per class (H 0.1 / K 0.2 / L 0.5).
0.2 mm at any diameter — one value per class (H 0.1 / K 0.2 / L 0.5).
Are GB/T 1804 and ISO 2768-1 the same numbers?
Yes — f/m/c/v equivalent grades with identical values; GB/T 1804-2000 eqv ISO 2768-1:1989.
Yes — f/m/c/v equivalent grades with identical values; GB/T 1804-2000 eqv ISO 2768-1:1989.
JIS B 0405 vs ISO 2768-1 — any mapping gap?
None in values; JIS splits the parts into B 0405 (sizes) and B 0419 (geometry) with identical tables.
None in values; JIS splits the parts into B 0405 (sizes) and B 0419 (geometry) with identical tables.
What flatness applies to an untoleranced 200 mm face under K?
0.4 mm (over 100 up to 300 length band, K grade).
0.4 mm (over 100 up to 300 length band, K grade).
Sheet-metal bracket — quote m or c?
c is the shop default for formed parts: ±1.2 mm on a 200 mm edge vs ±0.5 under m.
c is the shop default for formed parts: ±1.2 mm on a 200 mm edge vs ±0.5 under m.
What is the smallest band ISO 2768-1 covers?
0.5 up to 3 mm: ±0.05 (f) / ±0.1 (m) / ±0.2 (c); below 0.5 mm indicate individually.
0.5 up to 3 mm: ±0.05 (f) / ±0.1 (m) / ±0.2 (c); below 0.5 mm indicate individually.
Standards & Sources
- S1 — MISUMI technical digest of JIS B 0405 / B 0419 (1991) — all linear, chamfer, angular and geometry tables, checked value-by-value against ISO
- S2 — ISO 2768-2:1989 untoleranced geometry values and derivation rules (reprint)
- S3 — ISO 2768-1:1989 general tolerances (reprint; adoption map for GB/T 1804, DIN ISO 2768, EN 22768)
- S4 — JIS B 0405:1991 adoption of ISO 2768-1:1989 and scope
- S5 — ISO 2768 tables transcription (source of one side of the 0.06 / K0.1 conflicts)
- S6 — ISO 2768 tables transcription (source of the ±5 and L 0.5 variants, registered)
- S7 — GB/T 1184 digest (straightness/perpendicularity/symmetry/run-out + derivation rules)
- S8 — JIS B 0419:1991 correspondence to ISO 2768-2:1989; run-out H 0.1 / K 0.2 / L 0.5
- S9 — GB/T 1184-1996 ebook cover confirmation (eqv ISO 2768-2:1989)
- S10 — ISO 2768-2:1989 catalogue entry, iso.org/standard/7749.html (withdrawn status)
- S11 — Integrated ISO 2768 entry, iso.org/standard/85741.html (under publication)
- S12 — GB/T 1804-2000 linear/chamfer tables (independent cross-check)
- S13 — GB/T 1184 K-grade shop practice cross-check
- S14 — DIN ISO 2768 T1/T2 adoption evidence (Maryland Metrics transcription)
- ISO 22081:2021 (GPS — general geometrical specifications) — the successor of ISO 2768-2:1989 for untoleranced geometry; H/K/L values carried over
Related Pages
- /wiki/tolerances/iso-2768/ — Long-form ISO 2768 guide on the same standard
- /wiki/reference/standard-tolerances/ — Sibling quick table: ISO 2768 grades plus IT grades for individually toleranced work
- /wiki/dfm/tolerance-design/ — How to assign tolerances so the shop can actually hold them