---
type: "fit-designation"
designation: "H9"
letter: "H"
it_grade: "ITIT9"
feature: "hole"
role: "Basic hole for free running fits with generous clearance."
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/h9
---

# H9 Tolerance — ISO 286 Hole Limits by Nominal Size

A 25 mm H9 hole runs 25.000 to 25.052 mm — deviations +0 to +52 µm on a 52 µm band. H9 is the ISO 286 hole tolerance built from fundamental deviation H and standard tolerance grade ITIT9. Basic hole for free running fits with generous clearance.

- **Designation**: H9
- **Feature**: hole
- **Fundamental deviation**: H — Zero deviation — the basic hole
- **Tolerance grade**: ITIT9
- **Typical use**: Basic hole for free running fits with generous clearance.
- **Standard**: ISO 286-1:2010, ISO 286-2:2010

## H9 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 hole Ø (mm) | Max hole Ø (mm) | IT tolerance (µm) |
| --- | --- | --- | --- | --- | --- |
| 5 mm | +30 | +0 | 5.000 | 5.030 | 30 |
| 6 mm | +30 | +0 | 6.000 | 6.030 | 30 |
| 8 mm | +36 | +0 | 8.000 | 8.036 | 36 |
| 10 mm | +36 | +0 | 10.000 | 10.036 | 36 |
| 12 mm | +43 | +0 | 12.000 | 12.043 | 43 |
| 16 mm | +43 | +0 | 16.000 | 16.043 | 43 |
| 20 mm | +52 | +0 | 20.000 | 20.052 | 52 |
| 25 mm | +52 | +0 | 25.000 | 25.052 | 52 |
| 30 mm | +52 | +0 | 30.000 | 30.052 | 52 |
| 40 mm | +62 | +0 | 40.000 | 40.062 | 62 |
| 50 mm | +62 | +0 | 50.000 | 50.062 | 62 |
| 80 mm | +74 | +0 | 80.000 | 80.074 | 74 |
| 100 mm | +87 | +0 | 100.000 | 100.087 | 87 |

_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 H9

### H9 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 H9 Tolerance

### What is an H9 tolerance?

H9 is an ISO 286 hole tolerance: fundamental deviation H at IT grade IT9. Basic hole for free running fits with generous clearance. Zero deviation — the basic hole describes what the H deviation does.

### What is the tolerance on a 25 mm H9 hole?

A 25 mm H9 hole runs 25.000 to 25.052 mm — deviations +0 to +52 µm, a tolerance band of 52 µm.

## Fits Built on H9

Standard hole/shaft pairs that use H9 as their hole.

| Fit | Classification | Basis | Typical use |
| --- | --- | --- | --- |
| [H9/d9](https://shopmath.org/fits/h9-d9.md) | Clearance | hole basis | Free running. Good where accuracy is not essential and clearance can be generous. |

## 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/h9) — data verified August 1, 2026. Reference data; verify against the governing standard before manufacture.*