Tolerance chart
H7 tolerance (hole): ISO 286 chart up to 500 mm
H7 is an ISO tolerance class for holes (internal features) under ISO 286. At Ø25 mm it means +21 / 0 µm: the size may lie between 25.000 and 25.021 mm. Below are the deviations for every nominal size up to 500 mm and the fits that use H7.
H7 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 | +10 | 0 | 10 |
| 3 – 6 | +12 | 0 | 12 |
| 6 – 10 | +15 | 0 | 15 |
| 10 – 18 | +18 | 0 | 18 |
| 18 – 30 | +21 | 0 | 21 |
| 30 – 50 | +25 | 0 | 25 |
| 50 – 80 | +30 | 0 | 30 |
| 80 – 120 | +35 | 0 | 35 |
| 120 – 180 | +40 | 0 | 40 |
| 180 – 250 | +46 | 0 | 46 |
| 250 – 315 | +52 | 0 | 52 |
| 315 – 400 | +57 | 0 | 57 |
| 400 – 500 | +63 | 0 | 63 |
H7 for your nominal size
How H7 is built
An ISO tolerance class is a letter and a number. Capital letters stand for holes, small letters for shafts. The letter H sets the position of the tolerance zone; at Ø25 mm it lies from the nominal size upwards: the hole is never 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 H7«; the inspection plan turns that into the limits 25.000 and 25.021 mm.
Fits with H7 at Ø25 mm
Hole-basis system: the hole stays H7, the shaft changes. Clearance in µm; a minus means interference. Sorted from the largest minimum clearance to the largest interference.
| Fit | Type | Max. clearance | Min. clearance |
|---|---|---|---|
| H7/e7 | clearance fit | 82 | 40 |
| H7/f6 | clearance fit | 54 | 20 |
| H7/f7 | clearance fit | 62 | 20 |
| H7/g6 | clearance fit | 41 | 7 |
| H7/h6 | clearance fit | 34 | 0 |
| H7/h7 | clearance fit | 42 | 0 |
| H7/js6 | transition fit | 27.5 | −6.5 |
| H7/k6 | transition fit | 19 | −15 |
| H7/m6 | transition fit | 13 | −21 |
| H7/n6 | transition fit | 6 | −28 |
| H7/p6 | interference fit | −1 | −35 |
| H7/r6 | interference fit | −7 | −41 |
| H7/s6 | interference fit | −14 | −48 |
Frequently asked questions about H7
What does H7 mean?
H7 is an ISO tolerance class for holes (internal features): the letter H sets the position of the tolerance zone, the number 7 the standard tolerance grade IT7. At Ø25 mm that gives +21 / 0 µm, i.e. 25.000 to 25.021 mm.
What are the H7 limits at Ø10 and Ø50 mm?
Ø10 H7: +15 / 0 µm (10.000 to 10.015 mm). Ø50 H7: +25 / 0 µm (50.000 to 50.025 mm).
Is H7 a clearance fit?
A tolerance class on its own is not a fit – only together with its mating part. H7/g6 at Ø25 mm is a clearance fit (maximum clearance 41 µm, minimum clearance 7 µm; a minus means interference).
More tolerance classes
Same letter H, other grades: H6 · H8 · H9 · H10 · H11
Holes in grade 7: G7 · F7 · JS7 · K7 · M7 · N7 · P7 · R7 · S7
All classes at a glance: ISO 286 tolerance charts. The same chart in German: H7 Toleranz.