What is the tolerance of a 25 mm H7 hole?

A 25 mm H7 hole runs 25.000 to 25.021 mm — deviations of 0 to +21 µm, a tolerance band 21 µm wide.

H7 is an ISO 286 hole tolerance. The H sets the fundamental deviation — zero deviation — the basic hole — and the 7 is the IT7 tolerance grade, which sets how wide the band is. The default basic hole in hole-basis fitting — reamer and gauge sizes are built around it.

How wide is the IT7 tolerance band?

IT7 is 21 µm wide for nominal sizes over 18 up to 30 mm, and widens with size — the full band table is on this page.

H7 appears in 7 standard ISO 286 fits: H7/h6 (clearance), H7/g6 (clearance), H7/p6 (interference), H7/r6 (interference), H7/k6 (transition), H7/m6 (transition), H7/n6 (transition).

Is there a H7 page for each nominal size?

Yes — H7 carries a page for each of the thirteen nominal sizes with verified demand, from 5 mm to 100 mm, each with the limits, the IT grades at that size and the fits available there.

ISO 286 · hole tolerance · IT7

H7 Tolerance — Hole Limits by Nominal Size

https://shopmath.org/fits/h7 · data verified August 1, 2026

A 25 mm H7 hole runs 25.000 to 25.021 mm — deviations of 0 to +21 µm on a tolerance band 21 µm wide. The H sets where the band sits (zero deviation — the basic hole) and IT7 sets how wide it is. The default basic hole in hole-basis fitting — reamer and gauge sizes are built around it. All values apply at 20 °C.

Feature: hole
Letter: H
Grade: IT7
Sizes: 13
Standard: ISO 286-1:2010

H7 hole at Ø25 mm · deviation, µm

+21 / 0

Max Ø: 25.021mm
Min Ø: 25.000mm
Band: 21µm

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

H7 Hole Limits at Every Verified Nominal Size

Deviations in micrometres and finished limits in millimetres. Every size links to its own page.

H7 hole tolerance — deviations and limits by nominal size
Property	Deviation, µm		Limits, mm		Property
Nominal Ø	Upper	Lower	Min	Max	Tolerance band, µm
5 mm	+12	0	5.000	5.012	12
6 mm	+12	0	6.000	6.012	12
8 mm	+15	0	8.000	8.015	15
10 mm	+15	0	10.000	10.015	15
12 mm	+18	0	12.000	12.018	18
16 mm	+18	0	16.000	16.018	18
20 mm	+21	0	20.000	20.021	21
25 mm	+21	0	25.000	25.021	21
30 mm	+21	0	30.000	30.021	21
40 mm	+25	0	40.000	40.025	25
50 mm	+25	0	50.000	50.025	25
80 mm	+30	0	80.000	80.030	30
100 mm	+35	0	100.000	100.035	35

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

The IT7 Tolerance Grade in H7, Across ISO 286 Size Bands

The number in H7 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.

IT7 standard tolerance by nominal size band
Nominal size band	Tolerance, µm	Tolerance, mm
over 0 to 3 mm	10	0.010
over 3 to 6 mm	12	0.012
over 6 to 10 mm	15	0.015
over 10 to 18 mm	18	0.018
over 18 to 30 mm	21	0.021
over 30 to 50 mm	25	0.025
over 50 to 80 mm	30	0.030
over 80 to 120 mm	35	0.035
over 120 to 180 mm	40	0.040
over 180 to 250 mm	46	0.046
over 250 to 315 mm	52	0.052
over 315 to 400 mm	57	0.057
over 400 to 500 mm	63	0.063

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 hole Tolerance in H7

The letter in H7 sets where the tolerance band sits relative to the nominal size: zero deviation — the basic hole. 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 lower limit (ei / EI) for every band, so IT7 alone decides how wide the band is. That is what makes H7 the basic hole: 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.

Standard Fits That Use the H7 Tolerance

A tolerance on its own is half a fit. These are the standard ISO 286 pairs H7 appears in, with what each one is used for.

Standard ISO 286 fits that use H7
Fit	Type	Basis	What it is for
H7/h6	clearance	hole or shaft	Locational clearance. Assembles by hand, no free movement intended.
H7/g6	clearance	hole basis	Sliding. Locates accurately, still moves and turns freely.
H7/p6	interference	hole basis	Locational interference. Rigid location in steel without the load capacity of a drive fit.
H7/r6	interference	hole basis	Medium drive. The joint itself carries load.
H7/k6	transition	hole basis	Locational transition. Accurate location, assembles with light force.
H7/m6	transition	hole basis	Locational transition, tighter than k6.
H7/n6	transition	hole basis	Tight transition. Usually a press job.

Clearance, transition and interference are properties of the pair, not of either tolerance alone.

Sources and Method for the H7 Tolerance Data

H7 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.

IT7 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, hole 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 H7 Tolerance Reference

Citation

ShopMath. "H7 Tolerance — Hole Limits by Nominal Size." ShopMath, verified August 1, 2026, https://shopmath.org/fits/h7

BibTeX

@misc{shopmath-fits-h7,
  title        = {H7 Tolerance — Hole Limits by Nominal Size},
  author       = {{ShopMath}},
  year         = {2026},
  howpublished = {\url{https://shopmath.org/fits/h7}},
  note         = {Data verified 2026-08-01}
}

Permanent URL

https://shopmath.org/fits/h7

Common Questions About the H7 Tolerance

What is the tolerance of a 25 mm H7 hole?: A 25 mm H7 hole runs 25.000 to 25.021 mm — deviations of 0 to +21 µm, a tolerance band 21 µm wide.
What does H7 mean?: H7 is an ISO 286 hole tolerance. The H sets the fundamental deviation — zero deviation — the basic hole — and the 7 is the IT7 tolerance grade, which sets how wide the band is. The default basic hole in hole-basis fitting — reamer and gauge sizes are built around it.
How wide is the IT7 tolerance band?: IT7 is 21 µm wide for nominal sizes over 18 up to 30 mm, and widens with size — the full band table is on this page.
Which fits use H7?: H7 appears in 7 standard ISO 286 fits: H7/h6 (clearance), H7/g6 (clearance), H7/p6 (interference), H7/r6 (interference), H7/k6 (transition), H7/m6 (transition), H7/n6 (transition).
Is there a H7 page for each nominal size?: Yes — H7 carries a page for each of the thirteen nominal sizes with verified demand, from 5 mm to 100 mm, each with the limits, the IT grades at that size and the fits available there.

Every ISO 286 designation and fit · ISO 286 tolerance chart