ISO 286 tolerance grade (IT) chart

The width of each tolerance grade in microns, by nominal size. This is the table behind every H7/g6 style fit callout on a drawing.

Sized for a single A4 sheet. Useful next to a CMM or inspection bench. Free to print, copy and hand out — no permission needed.

Tolerance width in microns (µm). 1 µm = 0.001 mm. Nominal size in mm, over–up to.
Size range	IT5	IT6	IT7	IT8	IT9	IT10	IT11
1–3	4	6	10	14	25	40	60
3–6	5	8	12	18	30	48	75
6–10	6	9	15	22	36	58	90
10–18	8	11	18	27	43	70	110
18–30	9	13	21	33	52	84	130
30–50	11	16	25	39	62	100	160
50–80	13	19	30	46	74	120	190
80–120	15	22	35	54	87	140	220
120–180	18	25	40	63	100	160	250
180–250	20	29	46	72	115	185	290
250–315	23	32	52	81	130	210	320
315–400	25	36	57	89	140	230	360
400–500	27	40	63	97	155	250	400

What the grades mean in practice. IT5–IT6 is ground or precision-bored work, typical of bearing seats. IT7 is the everyday precision-machining grade and the one most H7 holes are cut to. IT8–IT9 is general machining. IT10–IT11 covers non-critical features where a general tolerance would do the job.
The cost curve is steep. Each step down roughly doubles the difficulty — the jump from IT7 to IT6 often means a second operation or a different process entirely. If a feature does not need it, that is one of the largest savings available on any drawing.
Work out actual limits and clearances with the ISO 286 limits & fits calculator, or general tolerances with the ISO 2768 calculator.

ISO 286 tolerance grade (IT) chart — free reference from Dalloway Precision Engineering Ltd, a UK CNC machine shop. Interactive version and 32 more free calculators at dalloways.com/tools · no sign-up. Figures are typical reference values; the governing standard or your material certificate takes precedence.

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