Clearance fit
The smallest permitted hole is at least as large as the largest permitted shaft. Every in-tolerance assembly has zero or positive clearance.
ENGINEERING TOOL · ISO 286
ISO 286 fits & tolerance calculator
Calculate a single hole or shaft tolerance from callouts such as Ø25 g6, or pair both classes to analyze an ISO 286 fit such as Ø25 H7/g6.Runs locally in your browserNo upload. No sign-in. Instant results.
QUICK ANSWER · 25 MM EXAMPLELowercase g = shaft
25 g6 tolerance — quick answer
For a nominal 25 mm shaft in ISO 286 g6, the upper deviation es is −7 µm and the lower deviation ei is −20 µm. The permitted shaft size is 24.980–24.993 mm. Lowercase g denotes a shaft tolerance zone.
When paired with an H7 hole, the hole limits are 25.000–25.021 mm and the resulting clearance is 0.007–0.041 mm.
ISO 286 ENGINEERING LOOKUP
Enter a callout or use advanced inputs.
FIT ANALYSISØ25 H7/g6
Clearance fitNominal size25.000 mm
IT tolerance size band>18–30 mm
Result modeHole and shaft fit
| Feature | Designation | Lower deviation | Upper deviation | Minimum size | Maximum size | Total tolerance | Pre-coating range |
|---|---|---|---|---|---|---|---|
| Hole | H7 | 0 µm | +21 µm | 25.000 mm | 25.021 mm | 21 µm | — |
| Shaft | g6 | −20 µm | −7 µm | 24.980 mm | 24.993 mm | 13 µm | — |
Permitted size—
Minimum clearance0.007 mm
Maximum clearance0.041 mm
The hole remains larger than the shaft across both dimensional tolerance zones.
TOLERANCE-ZONE DIAGRAMPosition relative to the nominal zero line
µm from nominal · final dimensions also described in mmMEASURED VALUE CHECK
Screen measured diameters against these limits.
Dimensional screening only. Final acceptance depends on the drawing, measurement method, uncertainty, temperature, surface condition and agreed inspection requirements.
HOW TO USE THE CALCULATOR
From an ISO fit callout to usable machining limits.
ISO 286 separates a tolerance class into a letter and an IT grade. The calculator combines the selected hole and shaft classes at the nominal diameter, then reports the worst-case assembled fit.- 01
Enter the nominal diameter
Use the common basic size of the mating hole and shaft. Switch between millimetres and inches without changing the ISO tolerance class.
- 02
Select both tolerance classes
Choose the uppercase hole code and grade, then the lowercase shaft code and grade. The available grades follow the selected zone and size.
- 03
Read and copy the result
Use the deviations and absolute limits for machining or inspection. The fit range automatically identifies clearance, transition or interference.
WORKED ISO 286 EXAMPLES
Common 25 mm fits compared at their worst-case limits.
| Fit callout | Hole limits | Shaft limits | Fit range (hole − shaft) | Classification |
|---|---|---|---|---|
| Ø25 H7/g6 | 25.000–25.021 mm | 24.980–24.993 mm | +0.007 to +0.041 mm | Clearance fit |
| Ø25 H7/h6 | 25.000–25.021 mm | 24.987–25.000 mm | 0.000 to +0.034 mm | Clearance fit |
| Ø25 H7/k6 | 25.000–25.021 mm | 25.002–25.015 mm | −0.015 to +0.019 mm | Transition fit |
| Ø25 H7/p6 | 25.000–25.021 mm | 25.022–25.035 mm | −0.035 to −0.001 mm | Interference fit |
A positive result is clearance; a negative result is interference. Values are reference calculations and should be checked against the controlled drawing and licensed standard data for critical work.
INDEXABLE ISO 286 REFERENCE TABLES
ISO 286 tolerance class charts
Hole tolerance charts
Shaft tolerance charts
- c11Shaft limits by size
- d9Shaft limits by size
- f7Shaft limits by size
- g6Shaft limits by size
- h6Shaft limits by size
- k6Shaft limits by size
- n6Shaft limits by size
- p6Shaft limits by size
- s6Shaft limits by size
- u6Shaft limits by size
- h7Shaft limits by size
- h8Shaft limits by size
- h9Shaft limits by size
- h11Shaft limits by size
- f6Shaft limits by size
- f9Shaft limits by size
- m6Shaft limits by size
HOW TO READ H7/g6
The letter places the zone. The number sets its width.
HHole zone
lower deviation at nominal
lower deviation at nominal
7Hole IT grade
tolerance width
/tolerance width
gShaft zone
below nominal
below nominal
6Shaft IT grade
tolerance width
tolerance width
Transition fit
The hole and shaft tolerance zones overlap. Depending on the actual measured sizes, assembly may have a small clearance or a small interference.
Interference fit
The largest permitted hole remains smaller than the smallest permitted shaft. Assembly requires force, temperature difference or another controlled method.
HOLE-BASIS SYSTEM
Keep the H hole; change the shaft class.
In an H tolerance zone the hole's lower deviation is zero. Combinations such as H7/g6, H7/k6 and H7/p6 change the fit by moving the shaft tolerance zone.SHAFT-BASIS SYSTEM
Keep the h shaft; change the hole class.
In an h tolerance zone the shaft's upper deviation is zero. This approach is useful when a common shaft size must mate with holes requiring different fits.USE THE RESULT WELL
A diameter limit is only one part of a functional fit.
Drawing definition
Confirm the nominal size, tolerance symbols and applicable standard revision on the controlled drawing.
Geometry and texture
Roundness, cylindricity, position, runout and surface texture can affect function even when two-point size is within limits.
Finishing and inspection
Account for coating, temperature, measuring method and uncertainty. Use only supplier-confirmed net dimensional change for the optional pre-coating range.
ISO FITS FAQ
Questions engineers and buyers ask before releasing a drawing.
What is the tolerance for a 25 g6 shaft?
For a nominal 25 mm shaft, ISO 286 g6 gives an upper deviation es of −7 µm and a lower deviation ei of −20 µm. The permitted shaft size is 24.980–24.993 mm.
Is g6 a hole or shaft tolerance?
Lowercase g6 is a shaft tolerance class. Uppercase G6 is a hole tolerance class. Letter case is part of the ISO 286 designation and must not be changed.
What clearance does 25 H7/g6 produce?
At 25 mm, an H7 hole is 25.000–25.021 mm and a g6 shaft is 24.980–24.993 mm. The resulting worst-case diametral clearance is 0.007–0.041 mm.
What is the difference between clearance, transition and interference fits?
A clearance fit keeps the permitted hole at least as large as the permitted shaft. A transition fit has overlapping tolerance zones, so measured parts may assemble with clearance or interference. An interference fit keeps the permitted shaft larger than the permitted hole.
Can ISO 286 limits be displayed in inches?
Yes. The calculator converts the entered nominal size, deviations, limits and fit range for display in inches. The tolerance classes remain ISO 286 classes; this does not convert them into ANSI B4.1 fit classes.
Does an in-tolerance diameter guarantee a functional fit?
No. This tool screens size only. Final acceptance depends on the controlled drawing, measurement method and uncertainty, temperature, surface condition, geometry, texture and agreed inspection requirements.
REFERENCE BASIS