What is the tolerance of a 25 mm h9 shaft?

A 25 mm h9 shaft runs 24.948 to 25.000 mm — deviations of -52 to 0 µm, a tolerance band 52 µm wide.

h9 is an ISO 286 shaft tolerance. The h sets the fundamental deviation — zero deviation — the basic shaft — and the 9 is the IT9 tolerance grade, which sets how wide the band is. Basic shaft for shaft-basis free running fits.

How wide is the IT9 tolerance band?

IT9 is 52 µm wide for nominal sizes over 18 up to 30 mm, and widens with size — the full band table is on this page.

ISO 286 · shaft tolerance · IT9

h9 Tolerance — Shaft Limits by Nominal Size

https://shopmath.org/fits/h9-shaft · data verified August 1, 2026

A 25 mm h9 shaft runs 24.948 to 25.000 mm — deviations of -52 to 0 µm on a tolerance band 52 µm wide. The h sets where the band sits (zero deviation — the basic shaft) and IT9 sets how wide it is. Basic shaft for shaft-basis free running fits. All values apply at 20 °C.

Feature: shaft
Letter: h
Grade: IT9
Sizes: 13
Standard: ISO 286-1:2010

h9 shaft at Ø25 mm · deviation, µm

0 / -52

Max Ø: 25.000mm
Min Ø: 24.948mm
Band: 52µm

Deviations from the 25 mm nominal size, at 20 °C. Every other verified size is in the table below.

Source: ISO 286-1:2010, ISO 286-2:2010
Formula: max Ø = nominal + es min Ø = nominal + ei
Assumptions: Ø25 mm nominal, 18–30 mm size step, plain cylindrical feature, 20 °C. Deviations are tabulated in the standard and compiled here; the limits are those deviations added to the nominal size.
Verified: August 1, 2026

h9 Shaft Limits at Every Verified Nominal Size

Deviations in micrometres and finished limits in millimetres. These are the thirteen nominal sizes with verified demand; the deviation pattern continues across the full ISO 286 size range.

h9 shaft tolerance — deviations and limits by nominal size
Property	Deviation, µm		Limits, mm		Property
Nominal Ø	Upper	Lower	Min	Max	Tolerance band, µm
5 mm	0	-30	4.970	5.000	30
6 mm	0	-30	5.970	6.000	30
8 mm	0	-36	7.964	8.000	36
10 mm	0	-36	9.964	10.000	36
12 mm	0	-43	11.957	12.000	43
16 mm	0	-43	15.957	16.000	43
20 mm	0	-52	19.948	20.000	52
25 mm	0	-52	24.948	25.000	52
30 mm	0	-52	29.948	30.000	52
40 mm	0	-62	39.938	40.000	62
50 mm	0	-62	49.938	50.000	62
80 mm	0	-74	79.926	80.000	74
100 mm	0	-87	99.913	100.000	87

Deviations are relative to the nominal size: positive is above it, negative below. Limits assume the ISO 286 reference temperature of 20 °C.

The IT9 Tolerance Grade in h9, Across ISO 286 Size Bands

The number in h9 is the IT grade, and it sets how wide the tolerance band is. The band widens with size — that is the whole point of a graded tolerance system.

IT9 standard tolerance by nominal size band
Nominal size band	Tolerance, µm	Tolerance, mm
over 0 to 3 mm	25	0.025
over 3 to 6 mm	30	0.030
over 6 to 10 mm	36	0.036
over 10 to 18 mm	43	0.043
over 18 to 30 mm	52	0.052
over 30 to 50 mm	62	0.062
over 50 to 80 mm	74	0.074
over 80 to 120 mm	87	0.087
over 120 to 180 mm	100	0.100
over 180 to 250 mm	115	0.115
over 250 to 315 mm	130	0.130
over 315 to 400 mm	140	0.140
over 400 to 500 mm	155	0.155

Bands are open at the bottom and closed at the top: 'over 18 to 30 mm' includes 30 mm and excludes 18 mm.

Fundamental Deviation of the h shaft Tolerance in h9

The letter in h9 sets where the tolerance band sits relative to the nominal size: zero deviation — the basic shaft. The grade then adds the band width to that starting point.

h fundamental deviation

0µm

At every one of the 25 ISO 286 size bands, from 0 to 500 mm.

The h deviation does not change with size — it is the upper limit (es / ES) for every band, so IT9 alone decides how wide the band is. That is what makes h9 the basic shaft: one limit is pinned at the nominal size and the grade opens the other. Sizes are given in the limits table above, and the full band-by-band listing is in this page’s Markdown twin.

Sources and Method for the h9 Tolerance Data

h9 limitscomputed

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

Verified against parkergreene/isofits ISO 286-2 limit tables (MIT); ISO 286-1 formula harness — 2067 checks passed

Computed from the standard's formulas, then checked against published tables.

IT9 tolerance gradecompiled

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

Verified against parkergreene/isofits ISO 286-2 limit tables (MIT); ISO 286-1 formula harness — 2067 checks passed. Formula per ISO 286-1 standard tolerance factor and fundamental deviation formulas, used as a validation harness only per docs/research/data-sourcing.md §3.6

Compiled from independent public sources that agree cell-for-cell.

h fundamental deviationcompiled

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

Verified against parkergreene/isofits ISO 286-2 limit tables (MIT); ISO 286-1 formula harness — 2067 checks passed

Compiled from independent public sources that agree cell-for-cell.

Formula

Limits from the deviations, shaft tolerance

max Ø  =  nominal + es
min Ø  =  nominal + ei

  es = upper deviation (µm)
  ei = lower deviation (µm)

The deviations are tabulated in ISO 286-2 and compiled here; the limits are those deviations added to the nominal size, which is why both columns are shown.

Assumptions

Values apply at the ISO 286 reference temperature of 20 °C.
Limits are for a plain cylindrical feature. A tolerance letter says nothing about surface finish, form or roundness — those need their own callouts.
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

How this data is built and checked →

How to Cite This h9 Tolerance Reference

Citation

ShopMath. "h9 Tolerance — Shaft Limits by Nominal Size." ShopMath, verified August 1, 2026, https://shopmath.org/fits/h9-shaft

BibTeX

@misc{shopmath-fits-h9-shaft,
  title        = {h9 Tolerance — Shaft Limits by Nominal Size},
  author       = {{ShopMath}},
  year         = {2026},
  howpublished = {\url{https://shopmath.org/fits/h9-shaft}},
  note         = {Data verified 2026-08-01}
}

Permanent URL

https://shopmath.org/fits/h9-shaft

Common Questions About the h9 Tolerance

What is the tolerance of a 25 mm h9 shaft?: A 25 mm h9 shaft runs 24.948 to 25.000 mm — deviations of -52 to 0 µm, a tolerance band 52 µm wide.
What does h9 mean?: h9 is an ISO 286 shaft tolerance. The h sets the fundamental deviation — zero deviation — the basic shaft — and the 9 is the IT9 tolerance grade, which sets how wide the band is. Basic shaft for shaft-basis free running fits.
How wide is the IT9 tolerance band?: IT9 is 52 µm wide for nominal sizes over 18 up to 30 mm, and widens with size — the full band table is on this page.

Every ISO 286 designation and fit · ISO 286 tolerance chart