Hole & shaft fits calculator

Pick a size and a fit (for example H7/g6 for a sliding fit). It gives the largest and smallest hole and shaft, and how much clearance or interference you get.

Safety: press and shrink fits store a lot of energy. Use a press with guards, support the work properly, and wear gloves and eye protection when heating or freezing parts.

How it works, guides and notes

How it works

A fit is two tolerances: a letter that sets how far the zone sits from the nominal size (H holes start exactly on size), and a grade number that sets how wide it is (7 is a typical reamed or fine-bored hole, 6 a ground or finely turned shaft).

The tolerance width comes from the standard tolerance unit i = 0.45∛D + 0.001D µm, where D is the geometric mean of the size step (for example √(18 × 30) for 25 mm). IT6 is 10i, IT7 16i, IT8 25i and so on. Each shaft letter has its own formula for the deviation nearest the nominal size; holes D–G mirror their shaft letter.

Published tables round these to preferred values, so results here can differ by a micron or two (rarely three) from the printed tables. They are marked EST. For inspection or drawings, use the current ISO 286-2 tables.

Worked example: 25 mm H7/g6: hole 25.000 to 25.021, shaft 24.980 to 24.993, so 0.007 to 0.041 mm clearance: a precise sliding fit.

Hole-making tips: a reamed hole is typically H7 to H8, a drilled hole H11 to H12 at best. Bearing makers publish their own recommended shaft and housing fits, so use those for bearings.

Spotted a mistake? Report an error.