Mechanical Fits Calculator
Calculate ISO-style fits like H7/g6
Estimate hole limits, shaft limits, minimum clearance, maximum clearance, and fit type for common mechanical fit callouts.
Reference only. This is an ISO-style approximation and is not an exact ISO 286 table lookup. Use it to understand fit calculations, then verify released dimensions against the governing standard and drawing requirements.
Live calculator
Hole and shaft limits from a fit callout
Enter a basic size in millimeters and a fit callout such as H7/g6. The calculator estimates the tolerance zones and shows the resulting fit range.
Reference approximation only
This calculator explains how fits are estimated from ISO-style tolerance codes. It is not an exact ISO 286 table lookup and should not be used as released manufacturing authority. Verify final limits against the governing standard, drawing notes, and company practice.
Use a hole code and shaft code such as H7/g6. Compact inputs like H7g6 work too.
Fit type
Clearance fit
H7/g6 at 10 mm basic size.
Minimum clearance
0.005014 mm
0.000197 in
Maximum clearance
0.028366 mm
0.001117 in
Limit dimensions
| Feature | Code | Lower deviation | Upper deviation | Minimum size | Maximum size |
|---|---|---|---|---|---|
| Hole/internal feature | H7 | 0 um | 14.37 um | 10 mm | 10.01437 mm |
| Shaft/external feature | g6 | -13.996 um | -5.014 um | 9.986004 mm | 9.994986 mm |
How this estimate is calculated
- Find the diameter step for the basic size and calculate a standard tolerance width.
- Apply the hole and shaft tolerance zone offsets from the zero line.
- Subtract shaft maximum from hole minimum for minimum clearance.
- Subtract shaft minimum from hole maximum for maximum clearance.
Reference values
Reference diameter: 7.745967 mm
Diameter step: over 6 mm to 10 mm
Hole method: Hole H: lower deviation is on the zero line.
Shaft method: Shaft g: estimated upper deviation below basic size.
Examples
Fit types
Clearance, transition, and interference
A fit is calculated from the overlap between the internal feature limits and the external feature limits. The sign of the clearance range tells you how the parts can assemble.
Clearance fit
The smallest hole is still larger than the largest shaft. The result is always clearance.
Transition fit
The tolerance ranges overlap. Some parts may assemble with clearance and others may have interference.
Interference fit
The largest hole is still smaller than the smallest shaft. The result is always interference.
Calculation steps
How to calculate a fit
The core idea is simple: convert each tolerance code into limit dimensions, then compare the worst-case hole and shaft sizes.
- 1Start with the basic size, such as 10 mm.
- 2Parse the fit code into a hole tolerance class and shaft tolerance class, such as H7 and g6.
- 3Estimate each tolerance width from the ISO-style standard tolerance grade.
- 4Place each tolerance zone relative to the zero line using the letter position.
- 5Calculate hole minimum and maximum limits.
- 6Calculate shaft minimum and maximum limits.
- 7Minimum clearance is hole minimum minus shaft maximum.
- 8Maximum clearance is hole maximum minus shaft minimum.
FAQ
Mechanical fit calculator questions
Can this calculate H7/g6 fits?
Yes. Enter the basic size in millimeters and use H7/g6 as the fit callout. Compact input such as H7g6 also works.
Can I enter h7g6 in lowercase?
If the first code is lowercase, the calculator interprets it as the hole code in uppercase because a fit needs an internal feature and an external feature. For example, h7g6 is interpreted as H7/g6.
Is this an exact ISO 286 calculator?
No. This is a reference approximation that explains the calculation process and estimates common fits. Verify final limit deviations against ISO 286-2 or the governing standard before using values for manufacturing or inspection.
Which tolerance zones are supported?
The calculator supports H and JS hole zones, plus common shaft zones a, b, c, d, e, f, g, h, js, k, m, n, p, r, s, and u. H7/g6, H7/h6, H7/f7, H7/k6, and H7/p6 are included as examples.
Why are limits shown in millimeters and inches?
ISO-style fits are entered in millimeters, but inch equivalents are useful when discussing clearance or interference with inch-based teams or suppliers.
Sources
Official standards references
The calculator is an explanatory approximation. Use the governing standard and official tables for controlled values.
- ISO 286-1:2010
ISO describes Part 1 as the basis of tolerances, deviations, and fits, including concepts and terminology for linear sizes and basic hole/basic shaft principles.
- ISO 286-2:2010
ISO describes Part 2 as the tables of standard tolerance classes and limit deviations for holes and shafts.
- ISO 286-2 online browsing page
The public ISO browsing page summarizes the scope, notation, and use of upper and lower limit deviations for holes and shafts.