Tolerance chart

N7 tolerance (hole): ISO 286 chart up to 500 mm

N7 is an ISO tolerance class for holes (internal features) under ISO 286. At Ø25 mm it means −7 / −28 µm: the size may lie between 24.972 and 24.993 mm. Below are the deviations for every nominal size up to 500 mm and the fits that use N7.

Updated 2026-10-30 · Basis: ISO 286-1:2010 and ISO 286-2:2010 · irot Erstmuster

N7 chart: deviations for all nominal sizes up to 500 mm

Deviations in µm (1 µm = 0.001 mm). A nominal size belongs to the row »over … up to and including …«: exactly 30 mm is in the row ending at 30, 30.1 mm in the next one.

Nominal size over – to (mm)	Upper deviation	Lower deviation	Tolerance
0 – 3	−4	−14	10
3 – 6	−4	−16	12
6 – 10	−4	−19	15
10 – 18	−5	−23	18
18 – 30	−7	−28	21
30 – 50	−8	−33	25
50 – 80	−9	−39	30
80 – 120	−10	−45	35
120 – 180	−12	−52	40
180 – 250	−14	−60	46
250 – 315	−14	−66	52
315 – 400	−16	−73	57
400 – 500	−17	−80	63

N7 for your nominal size

How N7 is built

An ISO tolerance class is a letter and a number. Capital letters stand for holes, small letters for shafts. The letter N sets the position of the tolerance zone; at Ø25 mm it lies entirely below the nominal size: the hole is always smaller than nominal. The number 7 is the standard tolerance grade IT7: it sets how wide the zone is – 21 µm at Ø25 mm.

The tolerance grows with the nominal size: 10 µm in the smallest row (0 – 3 mm), 63 µm in the largest (400 – 500 mm). On a drawing the class follows the dimension, as in »Ø25 N7«; the inspection plan turns that into the limits 24.972 and 24.993 mm.

Fits with N7 at Ø25 mm

Shaft-basis system: the shaft is h, the hole N7. Clearance in µm; a minus means interference. Sorted from the largest minimum clearance to the largest interference.

Fit	Type	Max. clearance	Min. clearance
N7/h6	transition fit	6	−28
N7/h7	transition fit	14	−28

Frequently asked questions about N7

What does N7 mean?

N7 is an ISO tolerance class for holes (internal features): the letter N sets the position of the tolerance zone, the number 7 the standard tolerance grade IT7. At Ø25 mm that gives −7 / −28 µm, i.e. 24.972 to 24.993 mm.

What are the N7 limits at Ø10 and Ø50 mm?

Ø10 N7: −4 / −19 µm (9.981 to 9.996 mm). Ø50 N7: −8 / −33 µm (49.967 to 49.992 mm).

Is N7 a clearance fit?

A tolerance class on its own is not a fit – only together with its mating part. N7/h6 at Ø25 mm is a transition fit (maximum clearance 6 µm, minimum clearance −28 µm; a minus means interference).

More tolerance classes

Same letter N, other grades: N6

Holes in grade 7: H7 · G7 · F7 · JS7 · K7 · M7 · P7 · R7 · S7

All classes at a glance: ISO 286 tolerance charts. The same chart in German: N7 Toleranz.