What does IT7 mean in tolerance?

IT7 is a tolerance grade in ISO 286 — the seventh of eighteen grades from IT01 to IT18. It is the standard grade for close sliding fits. The actual tolerance depends on the nominal size: 10 µm at 3 mm, 21 µm at 30 mm and 63 µm at 500 mm.

What is the tolerance for h7?

h7 is IT7 with the h deviation, meaning the tolerance zone sits entirely below nominal size. On a 30 mm shaft that gives a tolerance width of 21 µm, with an upper deviation of zero and a lower deviation of −21 µm.

What is the difference between H7 and h7?

The letter case indicates hole or shaft. H7 is a hole with the zone above nominal; h7 is a shaft with the zone below. A 30H7 hole and a 30h7 shaft together give a clearance fit with zero minimum clearance.

What is the difference between h7 and g6?

Different grades and different positions. h7 is IT7 positioned below nominal; g6 is IT6 positioned further below, so it always produces clearance. A g6 shaft in an H7 hole is a standard clearance fit.

On a 25 mm diameter, IT7 is 21 µm total — about 0.0008 in. That is achievable by ordinary turning and reaming, and is the usual grade for a bearing seat or a close sliding fit.

What grade should I specify?

IT7 or IT8 for most machined fits, IT9 to IT11 for commercial work, and IT5 to IT6 only where precision genuinely requires it. Every grade tighter than IT8 adds cost disproportionately, so specify the coarsest grade the function allows.

ISO 286 Tolerance Chart

International Tolerance grade values in micrometres by nominal size range — the full range from IT01 to IT12, covering gauge work through general machining.

Page last changed 2026-10-19 · based on ISO 286-1:2010

Quick Answer

The IT number is a tolerance grade, not a tolerance. The value depends on the grade and the nominal size: IT7 is 10 µm on a 3 mm shaft but 30 µm on an 80 mm one. IT grades run IT01 to IT18 — IT7 and IT8 cover most general machining.

Find a size range

ISO 286 IT Grade Values (µm)

Nominal size mm^[1]	IT01^[1]	IT0^[1]	IT1^[1]	IT2^[1]	IT3^[1]	IT4^[1]	IT5^[1]	IT6^[1]	IT7^[1]	IT8^[1]	IT9^[1]	IT10^[1]	IT11^[1]	IT12^[1]
0–3 #	0.3	0.5	0.8	1.2	2	3	4	6	10	14	25	40	60	100
3–6 #	0.4	0.6	1	1.5	2.5	4	5	8	12	18	30	48	75	120
6–10 #	0.4	0.6	1	1.5	2.5	4	6	9	15	22	36	58	90	150
10–18 #	0.5	0.8	1.2	2	3	5	8	11	18	27	43	70	110	180
18–30 #	0.6	1	1.5	2.5	4	6	9	13	21	33	52	84	130	210
30–50 #	0.6	1	1.5	2.5	4	7	11	16	25	39	62	100	160	250
50–80 #	0.6	1.2	2	3	5	8	13	19	30	46	74	120	190	300
80–120 #	0.8	1.5	2.5	4	6	10	15	22	35	54	87	140	220	350
120–180 #	1	2	3.5	5	8	12	18	25	40	63	100	160	250	400
180–250 #	1.2	3	4.5	7	10	14	20	29	46	72	115	185	290	460
250–315 #	1.6	4	6	8	12	16	23	32	52	81	130	210	320	520
315–400 #	2	5	7	9	13	18	25	36	57	89	140	230	360	570
400–500 #	2.5	6	8	10	15	20	27	40	63	97	155	250	400	630

Values are total tolerance widths in micrometres. A grade applies to both holes and shafts; the deviation letters (h, H, g, f, p, etc.) determine where that tolerance sits relative to nominal size. Grades finer than IT5 are normally achieved by grinding, honing or lapping rather than by turning.

Grade and Deviation Are Different Things

An ISO 286 fit is written as a number and a letter: 30h7 or 30H7. These carry two independent pieces of information:

The number (IT grade) sets the width of the tolerance zone — how much variation is permitted. It comes from the table above.
The letter (deviation) sets the position of that zone relative to nominal size. Lower case is a shaft, upper case is a hole. h places the zone entirely below nominal; H entirely above; g and f shift it further down to create clearance; p and s shift it up to create interference.

So 30h7 and 30g7 have the same tolerance width — 21 µm — but sit in different places, and therefore produce different fits. The grade table alone cannot tell you whether a fit is clearance or interference.

Choosing a Grade

IT5–IT6 — precision fits, gauge work, bearing seats. Usually needs grinding or fine boring.
IT7–IT8 — the general machining range. IT7 is the standard for a close sliding fit and is achievable by turning, milling and reaming without special measures.
IT9–IT10 — commercial fits, non-critical location, stamping and general fabrication.
IT11–IT12 — coarse fits, clearance holes, welded assemblies.

The tolerance roughly doubles for every two grades, so moving from IT7 to IT9 more than doubles the permitted variation. Specify the coarsest grade the function allows — every step tighter costs disproportionately more to produce and inspect.

Frequently Asked Questions

What does IT7 mean in tolerance?: IT7 is a tolerance grade in ISO 286 — the seventh of eighteen grades from IT01 to IT18. It is the standard grade for close sliding fits. The actual tolerance depends on the nominal size: 10 µm at 3 mm, 21 µm at 30 mm and 63 µm at 500 mm.
What is the tolerance for h7?: h7 is IT7 with the h deviation, meaning the tolerance zone sits entirely below nominal size. On a 30 mm shaft that gives a tolerance width of 21 µm, with an upper deviation of zero and a lower deviation of −21 µm.
What is the difference between H7 and h7?: The letter case indicates hole or shaft. H7 is a hole with the zone above nominal; h7 is a shaft with the zone below. A 30H7 hole and a 30h7 shaft together give a clearance fit with zero minimum clearance.
What is the difference between h7 and g6?: Different grades and different positions. h7 is IT7 positioned below nominal; g6 is IT6 positioned further below, so it always produces clearance. A g6 shaft in an H7 hole is a standard clearance fit.
How tight is IT7?: On a 25 mm diameter, IT7 is 21 µm total — about 0.0008 in. That is achievable by ordinary turning and reaming, and is the usual grade for a bearing seat or a close sliding fit.
What grade should I specify?: IT7 or IT8 for most machined fits, IT9 to IT11 for commercial work, and IT5 to IT6 only where precision genuinely requires it. Every grade tighter than IT8 adds cost disproportionately, so specify the coarsest grade the function allows.

Value Sources

References and calculation methods used for this page are listed below. Numbered markers connect table columns where present. A reference listing does not itself establish that every value has been independently checked.

#	Source	Type	Revision / method
[1]	ISO 286-1 — ISO code system for tolerances on linear sizes	reference	ISO 286-1:2010 — source

Data Sources

Standard	Revision	What it covers on this page
ISO 286-1 — ISO code system for tolerances on linear sizes	ISO 286-1:2010	the IT grade values and the nominal size ranges on this page

Verification scope

No page-specific independent source review is recorded here. The listed references and formulas explain the basis of the compilation; automated consistency checks do not verify the original sources or establish product conformity.

Grade widths only. The deviation letters — h, H, g, f, p, s and the rest — set where the zone sits and are not reproduced here; obtain them from ISO 286-2. A fit cannot be designed from the grade table alone.

Accuracy and use. Use the source notes and recorded verification scope above to assess each value. Calculated values follow the stated derivations; compilation values may lack a confirmed original document or product condition. No warranty, express or implied, is made as to the accuracy or completeness of this information, and no liability is accepted for any loss or damage arising from its use. Engineering reference data is provided for guidance in preliminary work — before a value is used for design, fabrication or acceptance testing, verify it against the current revision of the governing standard and against your own inspection. The user assumes all risk and responsibility in connection with the use of this information.

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Read the source notes, calculation methods and verification scope above before reusing a value. To cite this page:

Plain text

Engineering Reference. "Tolerance Chart (ISO 286)." https://refmanual.com/charts/tolerances/ (accessed 2026-10-19). Data from ISO 286-1 — ISO code system for tolerances on linear sizes, ISO 286-1:2010.

BibTeX

@misc{tolerances,
  title        = {Tolerance Chart (ISO 286)},
  author       = {{Engineering Reference}},
  howpublished = {\url{https://refmanual.com/charts/tolerances/}},
  note         = {Accessed: 2026-10-19},
  source       = {ISO 286-1 — ISO code system for tolerances on linear sizes, ISO 286-1:2010}
}

RIS (EndNote, Zotero, Mendeley)

TY  - ELEC
TI  - Tolerance Chart (ISO 286)
AU  - Engineering Reference
PB  - Engineering Reference
UR  - https://refmanual.com/charts/tolerances/
PY  - 2026
DA  - 2026-10-19
N1  - Source: ISO 286-1 — ISO code system for tolerances on linear sizes, ISO 286-1:2010
ER  -

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