---
type: "fit-designation"
designation: "c11"
letter: "c"
it_grade: "ITIT11"
feature: "shaft"
role: "Loose running shaft for wide commercial tolerances and hot-running assemblies."
size_count: 13
size_range_mm: "5–100"
standard: "ISO 286-1:2010, ISO 286-2:2010"
verified: "August 1, 2026"
url: https://shopmath.org/fits/c11
---

# c11 Tolerance — ISO 286 Shaft Limits by Nominal Size

A 25 mm c11 shaft runs 24.760 to 24.890 mm — deviations -240 to -110 µm on a 130 µm band. c11 is the ISO 286 shaft tolerance built from fundamental deviation c and standard tolerance grade ITIT11. Loose running shaft for wide commercial tolerances and hot-running assemblies.

- **Designation**: c11
- **Feature**: shaft
- **Fundamental deviation**: c — Loose running clearance
- **Tolerance grade**: ITIT11
- **Typical use**: Loose running shaft for wide commercial tolerances and hot-running assemblies.
- **Standard**: ISO 286-1:2010, ISO 286-2:2010

## c11 Limits and Deviations by Nominal Size

Deviations are in micrometres from the nominal size; limits are the finished diameters in millimetres. Sizes that carry their own page are linked.

| Nominal size | Upper deviation (µm) | Lower deviation (µm) | Min shaft Ø (mm) | Max shaft Ø (mm) | IT tolerance (µm) |
| --- | --- | --- | --- | --- | --- |
| 5 mm | -70 | -145 | 4.855 | 4.930 | 75 |
| 6 mm | -70 | -145 | 5.855 | 5.930 | 75 |
| 8 mm | -80 | -170 | 7.830 | 7.920 | 90 |
| 10 mm | -80 | -170 | 9.830 | 9.920 | 90 |
| 12 mm | -95 | -205 | 11.795 | 11.905 | 110 |
| 16 mm | -95 | -205 | 15.795 | 15.905 | 110 |
| 20 mm | -110 | -240 | 19.760 | 19.890 | 130 |
| 25 mm | -110 | -240 | 24.760 | 24.890 | 130 |
| 30 mm | -110 | -240 | 29.760 | 29.890 | 130 |
| 40 mm | -120 | -280 | 39.720 | 39.880 | 160 |
| 50 mm | -130 | -290 | 49.710 | 49.870 | 160 |
| 80 mm | -150 | -340 | 79.660 | 79.850 | 190 |
| 100 mm | -170 | -390 | 99.610 | 99.830 | 220 |

_ISO 286 tabulates deviations per size band, so a value holds across the whole band a nominal size falls in, not just at that exact diameter._

## Sources and Method for c11

### c11 deviations

- **Source**: limits computed from the compiled ISO 286 tables: ISO 286-1 IT grades and ISO 286-2 fundamental deviations, compiled from saucecode/ISO286 (LGPL-2.1) and parkergreene/isofits (MIT), cross-checked cell-for-cell
- **Method**: computed
- **Verified against**: parkergreene/isofits ISO 286-2 limit tables (MIT); ISO 286-1 formula harness — 2067 checks passed

### Assumptions

- Values are the ISO 286-2 tabulated limits, not the ISO 286-1 formula: the formula deviates from the table by up to 13.26% and is carried only as a validation harness.
- Limits are at 20 °C, the ISO 1 reference temperature.
- Dataset scope: COMPILED not computed: the ISO 286-1 formula deviates up to 13.26% from the table and is used only as a harness (warn >5%, fail >15%). EXCLUDED: shaft/hole letters s, t, u and the fits H7/s6, H7/t6, H7/u6 — no free source and an undetermined step constant in the formula.

**Data last verified**: August 1, 2026

## Common Questions About the c11 Tolerance

### What is an c11 tolerance?

c11 is an ISO 286 shaft tolerance: fundamental deviation c at IT grade IT11. Loose running shaft for wide commercial tolerances and hot-running assemblies. Loose running clearance describes what the c deviation does.

### What is the tolerance on a 25 mm c11 shaft?

A 25 mm c11 shaft runs 24.760 to 24.890 mm — deviations -240 to -110 µm, a tolerance band of 130 µm.

## Fits Built on c11

Standard hole/shaft pairs that use c11 as their shaft.

| Fit | Classification | Basis | Typical use |
| --- | --- | --- | --- |
| [H11/c11](https://shopmath.org/fits/h11-c11.md) | Clearance | hole basis | Loose running. Wide commercial tolerances, large clearance for dirt, paint and thermal growth. |

## Related pages

- All fits and tolerances: [ISO 286 fit reference](https://shopmath.org/fits.md)
- Full grade table: [ISO 286 tolerance chart](https://shopmath.org/charts/iso-tolerances.md)

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*Source: [ShopMath](https://shopmath.org/fits/c11) — data verified August 1, 2026. Reference data; verify against the governing standard before manufacture.*