ISO fits and tolerance grades table
IT5-IT11 tolerance grades by size, and the ten preferred hole-basis fits.
Standard tolerance grades (µm)
| Size (mm) | IT5 | IT6 | IT7 | IT8 | IT9 | IT10 | IT11 |
|---|---|---|---|---|---|---|---|
| up to 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 |
Preferred hole-basis fits
| Fit | Name | Type | Clearance at 25 mm (µm, minus = interference) | Use |
|---|---|---|---|---|
| H11/c11 | Loose running | clearance | +110 to +370 | wide commercial tolerances, or allowances on external members |
| H9/d9 | Free running | clearance | +65 to +169 | not for accuracy; large temperature changes, high speeds or heavy journal pressure |
| H8/f7 | Close running | clearance | +20 to +74 | accurate location at moderate speeds and journal pressures |
| H7/g6 | Sliding | clearance | +7 to +41 | not meant to run freely, but to move and turn freely and locate accurately |
| H7/h6 | Locational clearance | clearance | +0 to +34 | snug fit for stationary parts that can still be freely assembled and taken apart |
| H7/k6 | Locational transition | transition | -15 to +19 | accurate location, a compromise between clearance and interference |
| H7/n6 | Locational transition | transition | -28 to +6 | more accurate location where more interference is acceptable |
| H7/p6 | Locational interference | interference | -35 to -1 | rigidity and alignment with accurate location, without special bore pressure |
| H7/s6 | Medium drive | interference | -48 to -14 | ordinary steel parts or shrink fits on light sections; the tightest usable with cast iron |
| H7/u6 | Force | interference | -61 to -27 | parts that can be highly stressed, or shrink fits where heavy pressing forces are impractical |
Source: ISO 286-1:2010 tables 1 and 2 (standard tolerance grades, fundamental deviations); the same values as ANSI B4.2-1978 preferred metric fits. Any size: ISO fit calculator.