Limits & Fits Calculator (ISO 286)
Enter a basic size and tolerance class (H7, g6…) to get the limits and the type of fit
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Enter a nominal size and the tolerance classes of a hole and a shaft (H7, g6 and so on) to get the limit deviations, the limits of size and the type of fit according to ISO 286. Use it when designing or checking fits of shafts and holes.
How to use
- On the "Fit" tab, enter the "Nominal size". Change the "Display unit" to see inches.
- Choose the "Hole letter", "Hole grade", "Shaft letter" and "Shaft grade", or press a pair such as H7/g6 under "Common fits".
- Read each part's "Upper limit deviation", "Lower limit deviation" and limits of size, the clearance or interference, and the type of fit.
- Find IT values on the "IT grade table" tab, and untoleranced dimensions on "General tolerances (ISO 2768-1)".
How it works
- Deviations come from the ISO 286-1 tables; hole deviations follow the rules of the standard (EI = −es and the Δ correction). Sizes above 0 up to 3150 mm are covered.
- Minimum clearance 0 or more means a clearance fit; maximum clearance 0 or less, an interference fit; otherwise a transition fit.
- General tolerances are Tables 1 to 3 of ISO 2768-1:1989. Calculations are in mm; inches are converted for display.
- For reference only. For contracts and inspections, check the text of the standard itself.
Questions and answers
- What are the limits of a 25 mm H7/g6 fit?
- The H7 hole is +21 to 0 µm and the g6 shaft −7 to −20 µm. The clearance is 7 to 41 µm, so it is a clearance fit.
- What is the difference between clearance, transition and interference fits?
- A clearance fit never has interference within the limits, and an interference fit never has clearance. A transition fit can have either, depending on the actual sizes.
- What do the letter and number in H7 mean?
- H is the position of the tolerance zone; an H hole has a lower deviation of 0. 7 is the IT grade; a larger number means a wider tolerance.
- What is general tolerance class m?
- The medium class of ISO 2768-1, for dimensions with no individual tolerance on the drawing. The "General tolerances (ISO 2768-1)" tab shows its value next to classes f, c and v.