What is H7 tolerance?

H7 is the ISO 286 basic hole: its lower deviation is zero and its upper deviation is the IT7 tolerance grade, so the hole is never smaller than the nominal size. At Ø25 mm an H7 hole runs 25.000 to 25.021 mm, a band of 21 µm.

What is the difference between a hole tolerance and a shaft tolerance?

Capital letters (H, G, F, K, N, P) are hole tolerances; lowercase letters (h, g, f, k, m, n, p, r) are shaft tolerances. The letter fixes the fundamental deviation — how far the tolerance band sits from the nominal size — and the number is the IT grade, which fixes how wide the band is.

What is the difference between a clearance, transition and interference fit?

The hole is always larger than the shaft — the parts always assemble with a gap. Depending on where each part lands in tolerance, the joint may end up with a small clearance or a small interference. The shaft is always larger than the hole — assembly needs force, heat or cold. This reference carries 16 standard pairs across the three.

Which nominal sizes have their own tolerance page?

The thirteen sizes with verified per-size demand: 5 mm, 6 mm, 8 mm, 10 mm, 12 mm, 16 mm, 20 mm, 25 mm, 30 mm, 40 mm, 50 mm, 80 mm, 100 mm. Every designation page carries all thirteen sizes in one table, and 6 designations also have a dedicated page per size.

Reference · ISO 286

ISO 286 Fits and Tolerances — H7, g6 and Every Designation

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

A Ø25 mm H7 hole runs 25.000 to 25.021 mm — 0 to +21 µm. 24 ISO 286 designations and 16 standard fit pairs, each with limits at 13 verified nominal sizes from 5 to 100 mm, in micrometres and millimetres. Deviations are compiled from ISO 286-2 tables, not reverse-engineered from a formula.

Designations: 24
Fit pairs: 16
Sizes: 13
Verified: August 1, 2026

ISO 286 Hole Tolerance Designations

Capital-letter designations, applied to the hole. Every row links to that designation's limits at all thirteen verified nominal sizes.

ISO 286 hole tolerance designations, with deviations at Ø25 mm
Property	Property	Property	Deviation at Ø25 mm, µm			Property
Designation	Applies to	Grade	Upper	Lower	Band µm	What it is for
F8	hole	IT8	+53	+20	33	Close running hole for shaft-basis fits with lubrication.
G7	hole	IT7	+28	+7	21	Small positive clearance hole for shaft-basis sliding fits.
H11	hole	IT11	+130	0	130	Wide-tolerance basic hole for loose running fits and cold-finished stock.
H6	hole	IT6	+13	0	13	Precision basic hole for close-running and transition fits.
H7	hole	IT7	+21	0	21	The default basic hole in hole-basis fitting — reamer and gauge sizes are built around it.
H8	hole	IT8	+33	0	33	Basic hole where a close running fit is wanted but H7 is more precision than the job needs.
H9	hole	IT9	+52	0	52	Basic hole for free running fits with generous clearance.
K7	hole	IT7	+6	-15	21	Shaft-basis transition hole — locates accurately, still assembles with light force.
N7	hole	IT7	-7	-28	21	Shaft-basis transition hole biased toward interference.
P7	hole	IT7	-14	-35	21	Shaft-basis light interference hole.

Deviations are shown at Ø25 mm as a common reference point; every designation page carries all thirteen verified sizes. Positive is above the nominal size, negative below.

ISO 286 Shaft Tolerance Designations

Lowercase designations, applied to the shaft. h is the basic shaft — zero upper deviation, so the shaft is never larger than nominal.

ISO 286 shaft tolerance designations, with deviations at Ø25 mm
Property	Property	Property	Deviation at Ø25 mm, µm			Property
Designation	Applies to	Grade	Upper	Lower	Band µm	What it is for
c11	shaft	IT11	-110	-240	130	Loose running shaft for wide commercial tolerances and hot-running assemblies.
d9	shaft	IT9	-65	-117	52	Free running shaft where accuracy is not essential.
e8	shaft	IT8	-40	-73	33	Running shaft with generous clearance for lubrication at speed.
f7	shaft	IT7	-20	-41	21	Close running shaft — the standard choice for lubricated journals at moderate speed.
g6	shaft	IT6	-7	-20	13	Sliding shaft with minimal clearance — locates accurately and still moves freely.
h11	shaft	IT11	0	-130	130	Wide-tolerance basic shaft matching drawn or cold-finished bar.
h6	shaft	IT6	0	-13	13	Precision basic shaft — zero upper deviation, the reference for locational clearance fits.
h7	shaft	IT7	0	-21	21	Basic shaft one grade coarser than h6, for shaft-basis close running fits.
h9	shaft	IT9	0	-52	52	Basic shaft for shaft-basis free running fits.
k6	shaft	IT6	+15	+2	13	Transition shaft — accurate location, assembles and disassembles with light force.
m6	shaft	IT6	+21	+8	13	Transition shaft biased tighter than k6.
n6	shaft	IT6	+28	+15	13	Tight transition shaft — usually needs a press for assembly.
p6	shaft	IT6	+35	+22	13	Light interference shaft for locational press fits in steel.
r6	shaft	IT6	+41	+28	13	Medium drive shaft for interference fits that transmit load through the joint.

The letter sets where the band sits relative to the nominal size; the IT number sets how wide it is.

Standard ISO 286 Fit Pairs — Clearance, Transition and Interference

A fit is a hole tolerance paired with a shaft tolerance. Negative clearance is interference: the shaft is larger than the hole and the joint needs force, heat or cold.

Standard ISO 286 hole/shaft fit pairs, with clearance at Ø25 mm
Property	Property	Property	Clearance at Ø25 mm, µm		Property
Fit	Type	Basis	Min	Max	What it is for
H7/h6	clearance	hole or shaft	0	+34	Locational clearance. Assembles by hand, no free movement intended.
H11/c11	clearance	hole basis	+110	+370	Loose running. Wide commercial tolerances, large clearance for dirt, paint and thermal growth.
H7/g6	clearance	hole basis	+7	+41	Sliding. Locates accurately, still moves and turns freely.
H8/e8	clearance	hole basis	+40	+106	Running fit with room for a lubricant film at speed.
H8/f7	clearance	hole basis	+20	+74	Close running. The general-purpose lubricated journal fit.
H9/d9	clearance	hole basis	+65	+169	Free running. Good where accuracy is not essential and clearance can be generous.
H7/p6	interference	hole basis	-35	-1	Locational interference. Rigid location in steel without the load capacity of a drive fit.
H7/r6	interference	hole basis	-41	-7	Medium drive. The joint itself carries load.
H7/k6	transition	hole basis	-15	+19	Locational transition. Accurate location, assembles with light force.
H7/m6	transition	hole basis	-21	+13	Locational transition, tighter than k6.
H7/n6	transition	hole basis	-28	+6	Tight transition. Usually a press job.
F8/h7	clearance	shaft basis	+20	+74	Close running, shaft basis.
G7/h6	clearance	shaft basis	+7	+41	Sliding, shaft basis. The h6 shaft is the reference and the hole carries the clearance.
P7/h6	interference	shaft basis	-35	-1	Locational interference, shaft basis.
K7/h6	transition	shaft basis	-15	+19	Locational transition, shaft basis.
N7/h6	transition	shaft basis	-28	+6	Tight transition, shaft basis.

Clearance figures are at Ø25 mm; each fit page carries all thirteen sizes. A transition fit can land either side of zero depending on where the two parts fall in tolerance.

Common Questions About ISO 286 Fits and Tolerances

What is H7 tolerance?: H7 is the ISO 286 basic hole: its lower deviation is zero and its upper deviation is the IT7 tolerance grade, so the hole is never smaller than the nominal size. At Ø25 mm an H7 hole runs 25.000 to 25.021 mm, a band of 21 µm.
What is the difference between a hole tolerance and a shaft tolerance?: Capital letters (H, G, F, K, N, P) are hole tolerances; lowercase letters (h, g, f, k, m, n, p, r) are shaft tolerances. The letter fixes the fundamental deviation — how far the tolerance band sits from the nominal size — and the number is the IT grade, which fixes how wide the band is.
What is the difference between a clearance, transition and interference fit?: The hole is always larger than the shaft — the parts always assemble with a gap. Depending on where each part lands in tolerance, the joint may end up with a small clearance or a small interference. The shaft is always larger than the hole — assembly needs force, heat or cold. This reference carries 16 standard pairs across the three.
Which nominal sizes have their own tolerance page?: The thirteen sizes with verified per-size demand: 5 mm, 6 mm, 8 mm, 10 mm, 12 mm, 16 mm, 20 mm, 25 mm, 30 mm, 40 mm, 50 mm, 80 mm, 100 mm. Every designation page carries all thirteen sizes in one table, and 6 designations also have a dedicated page per size.

Sources and Method for the ISO 286 Tolerance Data

ISO 286 IT grades, fundamental deviations and fitscompiled

saucecode/ISO286 (LGPL-2.1) + parkergreene/isofits (MIT), cross-checked cell-for-cell

Verified against fits-iso286: 2067 checks passed across 3 harness(es)

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

Assumptions

Limits are for a plain cylindrical feature at 20 °C, the ISO 286 reference temperature.
Per-size pages exist for the thirteen nominal sizes with verified demand (5, 6, 8, 10, 12, 16, 20, 25, 30, 40, 50, 80, 100 mm). Every designation page carries all thirteen in one table.
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 ISO 286 Tolerance Reference

Citation

ShopMath. "ISO 286 Fits and Tolerances — H7, g6 and Every Designation." ShopMath, verified August 1, 2026, https://shopmath.org/fits

BibTeX

@misc{shopmath-fits,
  title        = {ISO 286 Fits and Tolerances — H7, g6 and Every Designation},
  author       = {{ShopMath}},
  year         = {2026},
  howpublished = {\url{https://shopmath.org/fits}},
  note         = {Data verified 2026-08-01}
}

Permanent URL

https://shopmath.org/fits