Engineering tool · ISO 286-1

Tolerance calculator.

Calculate the dimensional tolerance of a shaft or a hole according to ISO 286: select size, position, and grade to obtain maximum and minimum dimensions.

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Tolerance table: same position, other qualities

Class	Upper deviation	IT	Minimum dimension	Maximum dimension
H01	+0,6 µm	0,6 µm	25,000 mm	25,001 mm
H0	+1 µm	1 µm	25,000 mm	25,001 mm
H1	+1,5 µm	1,5 µm	25,000 mm	25,002 mm
H2	+2,5 µm	2,5 µm	25,000 mm	25,003 mm
H3	+4 µm	4 µm	25,000 mm	25,004 mm
H4	+6 µm	6 µm	25,000 mm	25,006 mm
H5	+9 µm	9 µm	25,000 mm	25,009 mm
H6	+13 µm	13 µm	25,000 mm	25,013 mm
H7	+21 µm	21 µm	25,000 mm	25,021 mm
H8	+33 µm	33 µm	25,000 mm	25,033 mm
H9	+52 µm	52 µm	25,000 mm	25,052 mm
H10	+84 µm	84 µm	25,000 mm	25,084 mm
H11	+130 µm	130 µm	25,000 mm	25,130 mm
H12	+210 µm	210 µm	25,000 mm	25,210 mm
H13	+330 µm	330 µm	25,000 mm	25,330 mm
H14	+520 µm	520 µm	25,000 mm	25,520 mm
H15	+840 µm	840 µm	25,000 mm	25,840 mm
H16	+1300 µm	1300 µm	25,000 mm	26,300 mm
H17	+2100 µm	2100 µm	25,000 mm	27,100 mm
H18	+3300 µm	3300 µm	25,000 mm	28,300 mm

Examples

How to read an ISO tolerance: H7, h6, g6

A dimension like Ø25 H7 has three parts: the nominal size (25 mm), the position of the tolerance zone relative to the zero line (letter: uppercase for holes, lowercase for shafts) and the quality or tolerance grade (number: the lower, the more precise).

H / h are the base positions: the H hole starts at the zero line and grows upwards; the h shaft starts at the zero line and goes down.
A to G / a to g provide clearance (larger hole, smaller shaft). K to ZC / k to zc invade the zero line: transition or interference.
At Proto&Go!, the reference for machining with a drawing is IT7 for metals and IT11 for engineering plastics. The team confirms the feasibility of the requested dimensions by reviewing the part.

What quality to request based on the process

Proto&Go! process	Part with drawing	Example at Ø25 mm
CNC machining in metal	IT7	H7 → from 25.000 to 25.021 mm
CNC machining in engineering plastics	IT11	H11 → from 25.000 to 25.130 mm

ISO 286 tolerance table by diameter: H7, H8, H11, h6, h7 and g6

Upper and lower deviation in microns (µm) for the most common classes: holes in capital letters and shafts in lower case. For example, Ø25 H7 is +21 / 0 µm. For another class or a specific size, use the calculator above.

Ø (mm)	H7	H8	H11	h6	h7	g6
≤ 3	+10 / 0	+14 / 0	+60 / 0	0 / −6	0 / −10	−2 / −8
3–6	+12 / 0	+18 / 0	+75 / 0	0 / −8	0 / −12	−4 / −12
6–10	+15 / 0	+22 / 0	+90 / 0	0 / −9	0 / −15	−5 / −14
10–18	+18 / 0	+27 / 0	+110 / 0	0 / −11	0 / −18	−6 / −17
18–30	+21 / 0	+33 / 0	+130 / 0	0 / −13	0 / −21	−7 / −20
30–50	+25 / 0	+39 / 0	+160 / 0	0 / −16	0 / −25	−9 / −25
50–80	+30 / 0	+46 / 0	+190 / 0	0 / −19	0 / −30	−10 / −29
80–120	+35 / 0	+54 / 0	+220 / 0	0 / −22	0 / −35	−12 / −34
120–180	+40 / 0	+63 / 0	+250 / 0	0 / −25	0 / −40	−14 / −39
180–250	+46 / 0	+72 / 0	+290 / 0	0 / −29	0 / −46	−15 / −44
250–315	+52 / 0	+81 / 0	+320 / 0	0 / −32	0 / −52	−17 / −49
315–400	+57 / 0	+89 / 0	+360 / 0	0 / −36	0 / −57	−18 / −54
400–500	+63 / 0	+97 / 0	+400 / 0	0 / −40	0 / −63	−20 / −60

Each row runs from above the first size up to and including the second. Values according to ISO 286-1.

Dimensional, general, and geometric tolerances

This calculator covers the dimensional tolerances for shafts and holes per ISO 286. Dimensions without specified tolerances follow the general tolerances ISO 2768 (e.g., ISO 2768-mK), and form and position tolerances follow the geometric tolerances per ISO 1101.

What does H7 mean for a hole and what are its limit sizes?

H7 defines the size tolerance of a hole. The letter H fixes the lower deviation at zero: the minimum size matches the nominal. The grade 7 determines the tolerance range according to the diameter. For example, a Ø25 H7 hole accepts sizes between 25.000 and 25.021 mm.

What is the difference between H7 for a hole and h6 for a shaft?

Uppercase letters identify hole tolerances and lowercase letters identify shafts. In H7, the hole can be equal to or larger than the nominal size; in h6, the shaft can be equal to or smaller. For the same nominal diameter, the H7/h6 combination has a minimum clearance of zero. Grades 7 and 6 determine the range of each tolerance.

How do I calculate the maximum and minimum sizes for a shaft or hole according to ISO 286?

In the Proto&Go! tolerance calculator, select shaft or hole and enter the nominal size, position, and tolerance grade. You will obtain the maximum and minimum sizes in millimeters and the deviations in microns. The table allows comparing the available grades for that position. The tool covers nominal sizes greater than zero up to 500 mm.