---
type: "fit-designation"
designation: "N7"
letter: "N"
it_grade: "ITIT7"
feature: "hole"
role: "Shaft-basis transition hole biased toward interference."
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/n7
---

# N7 Tolerance — ISO 286 Hole Limits by Nominal Size

A 25 mm N7 hole runs 24.972 to 24.993 mm — deviations -28 to -7 µm on a 21 µm band. N7 is the ISO 286 hole tolerance built from fundamental deviation N and standard tolerance grade ITIT7. Shaft-basis transition hole biased toward interference.

- **Designation**: N7
- **Feature**: hole
- **Fundamental deviation**: N — Tight transition
- **Tolerance grade**: ITIT7
- **Typical use**: Shaft-basis transition hole biased toward interference.
- **Standard**: ISO 286-1:2010, ISO 286-2:2010

## N7 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 | -4 | -16 | 4.984 | 4.996 | 12 |
| 6 mm | -4 | -16 | 5.984 | 5.996 | 12 |
| 8 mm | -4 | -19 | 7.981 | 7.996 | 15 |
| 10 mm | -4 | -19 | 9.981 | 9.996 | 15 |
| 12 mm | -5 | -23 | 11.977 | 11.995 | 18 |
| 16 mm | -5 | -23 | 15.977 | 15.995 | 18 |
| 20 mm | -7 | -28 | 19.972 | 19.993 | 21 |
| 25 mm | -7 | -28 | 24.972 | 24.993 | 21 |
| 30 mm | -7 | -28 | 29.972 | 29.993 | 21 |
| 40 mm | -8 | -33 | 39.967 | 39.992 | 25 |
| 50 mm | -8 | -33 | 49.967 | 49.992 | 25 |
| 80 mm | -9 | -39 | 79.961 | 79.991 | 30 |
| 100 mm | -10 | -45 | 99.955 | 99.990 | 35 |

_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 N7

### N7 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 N7 Tolerance

### What is an N7 tolerance?

N7 is an ISO 286 hole tolerance: fundamental deviation N at IT grade IT7. Shaft-basis transition hole biased toward interference. Tight transition describes what the N deviation does.

### What is the tolerance on a 25 mm N7 hole?

A 25 mm N7 hole runs 24.972 to 24.993 mm — deviations -28 to -7 µm, a tolerance band of 21 µm.

## Fits Built on N7

Standard hole/shaft pairs that use N7 as their hole.

| Fit | Classification | Basis | Typical use |
| --- | --- | --- | --- |
| [N7/h6](https://shopmath.org/fits/n7-h6.md) | Transition | shaft basis | Tight transition, shaft basis. |

## 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/n7) — data verified August 1, 2026. Reference data; verify against the governing standard before manufacture.*