ISO 286 is the international system of limits and fits for holes and shafts. Use the tables below to pick a fit such as H7/g6 or H7/p6, read the limit deviations for your size, and check the resulting clearance or interference. The values apply to parts made by CNC machining, rapid prototyping and low-volume manufacturing. All values are in micrometres (µm); 1 µm = 0.001 mm.
ISO 286 basics
ISO 286-1 defines the system: standard tolerance grades (IT) and the position of the tolerance zone (fundamental deviation). ISO 286-2 gives the tables of tolerance grades and limit deviations. A fit is written as hole / shaft, for example Ø25 H7/g6.
- IT grade (e.g. IT7): sets the width of the tolerance zone for a given size. Smaller number = tighter tolerance = higher cost.
- Fundamental deviation (letter): sets the position of the zone relative to the nominal size. Capital letters are for holes, lowercase letters are for shafts.
- Hole-basis system: the hole is always H (lower deviation 0) and the shaft letter changes. This is the most common system.
- Shaft-basis system: the shaft is always h (upper deviation 0) and the hole letter changes.
- Clearance, transition, interference: the shaft is always smaller than the hole, either can happen, or the shaft is always larger than the hole.
Table 1 - Standard tolerance grades IT5 to IT14 (µm)
| Nominal size (mm) | IT5 | IT6 | IT7 | IT8 | IT9 | IT10 | IT11 | IT12 | IT13 | IT14 |
|---|---|---|---|---|---|---|---|---|---|---|
| Up to 3 | 4 | 6 | 10 | 14 | 25 | 40 | 60 | 100 | 140 | 250 |
| Over 3 to 6 | 5 | 8 | 12 | 18 | 30 | 48 | 75 | 120 | 180 | 300 |
| Over 6 to 10 | 6 | 9 | 15 | 22 | 36 | 58 | 90 | 150 | 220 | 360 |
| Over 10 to 18 | 8 | 11 | 18 | 27 | 43 | 70 | 110 | 180 | 270 | 430 |
| Over 18 to 30 | 9 | 13 | 21 | 33 | 52 | 84 | 130 | 210 | 330 | 520 |
| Over 30 to 50 | 11 | 16 | 25 | 39 | 62 | 100 | 160 | 250 | 390 | 620 |
| Over 50 to 80 | 13 | 19 | 30 | 46 | 74 | 120 | 190 | 300 | 460 | 740 |
| Over 80 to 120 | 15 | 22 | 35 | 54 | 87 | 140 | 220 | 350 | 540 | 870 |
| Over 120 to 180 | 18 | 25 | 40 | 63 | 100 | 160 | 250 | 400 | 630 | 1000 |
| Over 180 to 250 | 20 | 29 | 46 | 72 | 115 | 185 | 290 | 460 | 720 | 1150 |
| Over 250 to 315 | 23 | 32 | 52 | 81 | 130 | 210 | 320 | 520 | 810 | 1300 |
| Over 315 to 400 | 25 | 36 | 57 | 89 | 140 | 230 | 360 | 570 | 890 | 1400 |
| Over 400 to 500 | 27 | 40 | 63 | 97 | 155 | 250 | 400 | 630 | 970 | 1550 |
The tolerance width is the same for the hole and the shaft in the same IT grade and size range. Typical process capability (guide only): grinding and honing IT5 – IT7, reaming and fine boring IT6 – IT8, turning and milling IT8 – IT10 (see our 5-axis CNC machining), drilling IT10 – IT12.
Table 2 - Preferred hole-basis and shaft-basis fits
| Fit type | Hole-basis | Shaft-basis | Typical use |
|---|---|---|---|
| Loose running | H11/c11 | C11/h11 | Wide commercial tolerances with a large clearance. Loose pivots, hinges, agricultural and general equipment. |
| Free running | H9/d9 | D9/h9 | Not for accurate fits. Suits high speeds, large temperature changes or heavy bearing loads. |
| Close running | H8/f7 | F8/h7 | Accurate machines at moderate speed and bearing pressure; accurate location with a running clearance. |
| Sliding | H7/g6 | G7/h6 | Parts that must turn or slide freely and still locate accurately. Not meant for free running. |
| Locational clearance | H7/h6 | H7/h6 | Snug fit for locating stationary parts. Easy to assemble and take apart by hand. |
| Locational transition | H7/k6 | K7/h6 | Accurate location with a small chance of either clearance or interference. |
| Locational transition (tight) | H7/n6 | N7/h6 | More accurate location than k6; light press is acceptable. Typically needs a press or hammer. |
| Locational interference | H7/p6 | P7/h6 | Rigid, well-aligned assemblies without special bore pressure requirements. Pressed together. |
| Medium drive | H7/s6 | S7/h6 | Permanent assembly of steel parts, shrink fit on light sections. |
| Force fit | H7/u6 | U7/h6 | Heavily stressed parts, or where a normal press force is not enough. Shrink or force fit. |
Clearance Transition Interference. H7/p6 is a transition fit below about 3 mm and an interference fit above that.
Online fit calculator
Enter the nominal diameter (over 0 up to 500 mm) and pick a preferred hole-basis fit.
Table 3 - Limit deviations for holes and shafts (µm)
Shown as upper / lower deviation. Size ranges are "over ... up to and including ..." in mm.
| Nominal size (mm) | H7 | H8 | H9 | H11 | c11 | d9 | f7 | g6 | h6 | k6 | n6 | p6 | s6 | u6 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Up to 3 | +10 / 0 | +14 / 0 | +25 / 0 | +60 / 0 | -60 / -120 | -20 / -45 | -6 / -16 | -2 / -8 | 0 / -6 | +6 / 0 | +10 / +4 | +12 / +6 | +20 / +14 | +24 / +18 |
| Over 3 to 6 | +12 / 0 | +18 / 0 | +30 / 0 | +75 / 0 | -70 / -145 | -30 / -60 | -10 / -22 | -4 / -12 | 0 / -8 | +9 / +1 | +16 / +8 | +20 / +12 | +27 / +19 | +31 / +23 |
| Over 6 to 10 | +15 / 0 | +22 / 0 | +36 / 0 | +90 / 0 | -80 / -170 | -40 / -76 | -13 / -28 | -5 / -14 | 0 / -9 | +10 / +1 | +19 / +10 | +24 / +15 | +32 / +23 | +37 / +28 |
| Over 10 to 14 | +18 / 0 | +27 / 0 | +43 / 0 | +110 / 0 | -95 / -205 | -50 / -93 | -16 / -34 | -6 / -17 | 0 / -11 | +12 / +1 | +23 / +12 | +29 / +18 | +39 / +28 | +44 / +33 |
| Over 14 to 18 | +18 / 0 | +27 / 0 | +43 / 0 | +110 / 0 | -95 / -205 | -50 / -93 | -16 / -34 | -6 / -17 | 0 / -11 | +12 / +1 | +23 / +12 | +29 / +18 | +39 / +28 | +44 / +33 |
| Over 18 to 24 | +21 / 0 | +33 / 0 | +52 / 0 | +130 / 0 | -110 / -240 | -65 / -117 | -20 / -41 | -7 / -20 | 0 / -13 | +15 / +2 | +28 / +15 | +35 / +22 | +48 / +35 | +54 / +41 |
| Over 24 to 30 | +21 / 0 | +33 / 0 | +52 / 0 | +130 / 0 | -110 / -240 | -65 / -117 | -20 / -41 | -7 / -20 | 0 / -13 | +15 / +2 | +28 / +15 | +35 / +22 | +48 / +35 | +61 / +48 |
| Over 30 to 40 | +25 / 0 | +39 / 0 | +62 / 0 | +160 / 0 | -120 / -280 | -80 / -142 | -25 / -50 | -9 / -25 | 0 / -16 | +18 / +2 | +33 / +17 | +42 / +26 | +59 / +43 | +76 / +60 |
| Over 40 to 50 | +25 / 0 | +39 / 0 | +62 / 0 | +160 / 0 | -130 / -290 | -80 / -142 | -25 / -50 | -9 / -25 | 0 / -16 | +18 / +2 | +33 / +17 | +42 / +26 | +59 / +43 | +86 / +70 |
| Over 50 to 65 | +30 / 0 | +46 / 0 | +74 / 0 | +190 / 0 | -140 / -330 | -100 / -174 | -30 / -60 | -10 / -29 | 0 / -19 | +21 / +2 | +39 / +20 | +51 / +32 | +72 / +53 | +106 / +87 |
| Over 65 to 80 | +30 / 0 | +46 / 0 | +74 / 0 | +190 / 0 | -150 / -340 | -100 / -174 | -30 / -60 | -10 / -29 | 0 / -19 | +21 / +2 | +39 / +20 | +51 / +32 | +78 / +59 | +121 / +102 |
| Over 80 to 100 | +35 / 0 | +54 / 0 | +87 / 0 | +220 / 0 | -170 / -390 | -120 / -207 | -36 / -71 | -12 / -34 | 0 / -22 | +25 / +3 | +45 / +23 | +59 / +37 | +93 / +71 | +146 / +124 |
| Over 100 to 120 | +35 / 0 | +54 / 0 | +87 / 0 | +220 / 0 | -180 / -400 | -120 / -207 | -36 / -71 | -12 / -34 | 0 / -22 | +25 / +3 | +45 / +23 | +59 / +37 | +101 / +79 | +166 / +144 |
| Over 120 to 140 | +40 / 0 | +63 / 0 | +100 / 0 | +250 / 0 | -200 / -450 | -145 / -245 | -43 / -83 | -14 / -39 | 0 / -25 | +28 / +3 | +52 / +27 | +68 / +43 | +117 / +92 | +195 / +170 |
| Over 140 to 160 | +40 / 0 | +63 / 0 | +100 / 0 | +250 / 0 | -210 / -460 | -145 / -245 | -43 / -83 | -14 / -39 | 0 / -25 | +28 / +3 | +52 / +27 | +68 / +43 | +125 / +100 | +215 / +190 |
| Over 160 to 180 | +40 / 0 | +63 / 0 | +100 / 0 | +250 / 0 | -230 / -480 | -145 / -245 | -43 / -83 | -14 / -39 | 0 / -25 | +28 / +3 | +52 / +27 | +68 / +43 | +133 / +108 | +235 / +210 |
| Over 180 to 200 | +46 / 0 | +72 / 0 | +115 / 0 | +290 / 0 | -240 / -530 | -170 / -285 | -50 / -96 | -15 / -44 | 0 / -29 | +33 / +4 | +60 / +31 | +79 / +50 | +151 / +122 | +265 / +236 |
| Over 200 to 225 | +46 / 0 | +72 / 0 | +115 / 0 | +290 / 0 | -260 / -550 | -170 / -285 | -50 / -96 | -15 / -44 | 0 / -29 | +33 / +4 | +60 / +31 | +79 / +50 | +159 / +130 | +287 / +258 |
| Over 225 to 250 | +46 / 0 | +72 / 0 | +115 / 0 | +290 / 0 | -280 / -570 | -170 / -285 | -50 / -96 | -15 / -44 | 0 / -29 | +33 / +4 | +60 / +31 | +79 / +50 | +169 / +140 | +313 / +284 |
| Over 250 to 280 | +52 / 0 | +81 / 0 | +130 / 0 | +320 / 0 | -300 / -620 | -190 / -320 | -56 / -108 | -17 / -49 | 0 / -32 | +36 / +4 | +66 / +34 | +88 / +56 | +190 / +158 | +347 / +315 |
| Over 280 to 315 | +52 / 0 | +81 / 0 | +130 / 0 | +320 / 0 | -330 / -650 | -190 / -320 | -56 / -108 | -17 / -49 | 0 / -32 | +36 / +4 | +66 / +34 | +88 / +56 | +202 / +170 | +382 / +350 |
| Over 315 to 355 | +57 / 0 | +89 / 0 | +140 / 0 | +360 / 0 | -360 / -720 | -210 / -350 | -62 / -119 | -18 / -54 | 0 / -36 | +40 / +4 | +73 / +37 | +98 / +62 | +226 / +190 | +426 / +390 |
| Over 355 to 400 | +57 / 0 | +89 / 0 | +140 / 0 | +360 / 0 | -400 / -760 | -210 / -350 | -62 / -119 | -18 / -54 | 0 / -36 | +40 / +4 | +73 / +37 | +98 / +62 | +244 / +208 | +471 / +435 |
| Over 400 to 450 | +63 / 0 | +97 / 0 | +155 / 0 | +400 / 0 | -440 / -840 | -230 / -385 | -68 / -131 | -20 / -60 | 0 / -40 | +45 / +5 | +80 / +40 | +108 / +68 | +272 / +232 | +530 / +490 |
| Over 450 to 500 | +63 / 0 | +97 / 0 | +155 / 0 | +400 / 0 | -480 / -880 | -230 / -385 | -68 / -131 | -20 / -60 | 0 / -40 | +45 / +5 | +80 / +40 | +108 / +68 | +292 / +252 | +580 / +540 |
Table 4 - Maximum / minimum clearance (+) or interference (-) (µm)
| Nominal size (mm) | H11/c11 | H9/d9 | H8/f7 | H7/g6 | H7/h6 | H7/k6 | H7/n6 | H7/p6 | H7/s6 | H7/u6 |
|---|---|---|---|---|---|---|---|---|---|---|
| Up to 3 | +180 / +60 | +70 / +20 | +30 / +6 | +18 / +2 | +16 / 0 | +10 / -6 | +6 / -10 | +4 / -12 | -4 / -20 | -8 / -24 |
| Over 3 to 6 | +220 / +70 | +90 / +30 | +40 / +10 | +24 / +4 | +20 / 0 | +11 / -9 | +4 / -16 | 0 / -20 | -7 / -27 | -11 / -31 |
| Over 6 to 10 | +260 / +80 | +112 / +40 | +50 / +13 | +29 / +5 | +24 / 0 | +14 / -10 | +5 / -19 | 0 / -24 | -8 / -32 | -13 / -37 |
| Over 10 to 14 | +315 / +95 | +136 / +50 | +61 / +16 | +35 / +6 | +29 / 0 | +17 / -12 | +6 / -23 | 0 / -29 | -10 / -39 | -15 / -44 |
| Over 14 to 18 | +315 / +95 | +136 / +50 | +61 / +16 | +35 / +6 | +29 / 0 | +17 / -12 | +6 / -23 | 0 / -29 | -10 / -39 | -15 / -44 |
| Over 18 to 24 | +370 / +110 | +169 / +65 | +74 / +20 | +41 / +7 | +34 / 0 | +19 / -15 | +6 / -28 | -1 / -35 | -14 / -48 | -20 / -54 |
| Over 24 to 30 | +370 / +110 | +169 / +65 | +74 / +20 | +41 / +7 | +34 / 0 | +19 / -15 | +6 / -28 | -1 / -35 | -14 / -48 | -27 / -61 |
| Over 30 to 40 | +440 / +120 | +204 / +80 | +89 / +25 | +50 / +9 | +41 / 0 | +23 / -18 | +8 / -33 | -1 / -42 | -18 / -59 | -35 / -76 |
| Over 40 to 50 | +450 / +130 | +204 / +80 | +89 / +25 | +50 / +9 | +41 / 0 | +23 / -18 | +8 / -33 | -1 / -42 | -18 / -59 | -45 / -86 |
| Over 50 to 65 | +520 / +140 | +248 / +100 | +106 / +30 | +59 / +10 | +49 / 0 | +28 / -21 | +10 / -39 | -2 / -51 | -23 / -72 | -57 / -106 |
| Over 65 to 80 | +530 / +150 | +248 / +100 | +106 / +30 | +59 / +10 | +49 / 0 | +28 / -21 | +10 / -39 | -2 / -51 | -29 / -78 | -72 / -121 |
| Over 80 to 100 | +610 / +170 | +294 / +120 | +125 / +36 | +69 / +12 | +57 / 0 | +32 / -25 | +12 / -45 | -2 / -59 | -36 / -93 | -89 / -146 |
| Over 100 to 120 | +620 / +180 | +294 / +120 | +125 / +36 | +69 / +12 | +57 / 0 | +32 / -25 | +12 / -45 | -2 / -59 | -44 / -101 | -109 / -166 |
| Over 120 to 140 | +700 / +200 | +345 / +145 | +146 / +43 | +79 / +14 | +65 / 0 | +37 / -28 | +13 / -52 | -3 / -68 | -52 / -117 | -130 / -195 |
| Over 140 to 160 | +710 / +210 | +345 / +145 | +146 / +43 | +79 / +14 | +65 / 0 | +37 / -28 | +13 / -52 | -3 / -68 | -60 / -125 | -150 / -215 |
| Over 160 to 180 | +730 / +230 | +345 / +145 | +146 / +43 | +79 / +14 | +65 / 0 | +37 / -28 | +13 / -52 | -3 / -68 | -68 / -133 | -170 / -235 |
| Over 180 to 200 | +820 / +240 | +400 / +170 | +168 / +50 | +90 / +15 | +75 / 0 | +42 / -33 | +15 / -60 | -4 / -79 | -76 / -151 | -190 / -265 |
| Over 200 to 225 | +840 / +260 | +400 / +170 | +168 / +50 | +90 / +15 | +75 / 0 | +42 / -33 | +15 / -60 | -4 / -79 | -84 / -159 | -212 / -287 |
| Over 225 to 250 | +860 / +280 | +400 / +170 | +168 / +50 | +90 / +15 | +75 / 0 | +42 / -33 | +15 / -60 | -4 / -79 | -94 / -169 | -238 / -313 |
| Over 250 to 280 | +940 / +300 | +450 / +190 | +189 / +56 | +101 / +17 | +84 / 0 | +48 / -36 | +18 / -66 | -4 / -88 | -106 / -190 | -263 / -347 |
| Over 280 to 315 | +970 / +330 | +450 / +190 | +189 / +56 | +101 / +17 | +84 / 0 | +48 / -36 | +18 / -66 | -4 / -88 | -118 / -202 | -298 / -382 |
| Over 315 to 355 | +1080 / +360 | +490 / +210 | +208 / +62 | +111 / +18 | +93 / 0 | +53 / -40 | +20 / -73 | -5 / -98 | -133 / -226 | -333 / -426 |
| Over 355 to 400 | +1120 / +400 | +490 / +210 | +208 / +62 | +111 / +18 | +93 / 0 | +53 / -40 | +20 / -73 | -5 / -98 | -151 / -244 | -378 / -471 |
| Over 400 to 450 | +1240 / +440 | +540 / +230 | +228 / +68 | +123 / +20 | +103 / 0 | +58 / -45 | +23 / -80 | -5 / -108 | -169 / -272 | -427 / -530 |
| Over 450 to 500 | +1280 / +480 | +540 / +230 | +228 / +68 | +123 / +20 | +103 / 0 | +58 / -45 | +23 / -80 | -5 / -108 | -189 / -292 | -477 / -580 |
Maximum clearance = hole upper limit - shaft lower limit. Minimum clearance = hole lower limit - shaft upper limit. Negative values are interference.
How to use the tables
Example 1 - Ø25 H7/g6 (sliding fit)
| Deviation (µm) | Limits (mm) | |
|---|---|---|
| Hole H7 | +21 / 0 | 25.021 / 25.000 |
| Shaft g6 | -7 / -20 | 24.993 / 24.980 |
| Result | +41 / +7 (max / min clearance) | Clearance fit: 7 to 41 µm |
Example 2 - Ø25 H7/p6 (locational interference fit)
| Deviation (µm) | Limits (mm) | |
|---|---|---|
| Hole H7 | +21 / 0 | 25.021 / 25.000 |
| Shaft p6 | +35 / +22 | 25.035 / 25.022 |
| Result | -1 / -35 (max / min clearance) | Interference fit: 1 to 35 µm |
How to show fits on a drawing
On an assembly drawing write Ø25 H7/g6 (hole class first, then shaft class). On a part drawing write Ø25 H7 or Ø25 g6, optionally with the limits, for example Ø25 H7 (+0.021 / 0). Call out critical fits clearly so they can be checked at inspection (see our quality control process). Features without an individual tolerance fall under the general tolerances, see our ISO 2768 chart.
Design tips
- Use the preferred fits in Table 2 before creating a special combination.
- Only tighten a tolerance where the function needs it. Each step from IT8 to IT7 to IT6 raises machining and inspection cost.
- For press fits, also control surface finish, edge chamfers and material. Aluminium and steel behave differently, so check the fit for aluminum CNC machined parts separately.
- ISO 286 values apply at 20 °C. Check the fit at operating temperature for large parts or mixed materials.
