ISO 286 fit calculator

Choose the nominal size and the hole and shaft tolerance classes; deviations, limits of size and whether the fit is clearance, transition or interference follow at once. Values are computed with the ISO 286-1:2010 rules and tested against published ISO 286-2 tables.

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Nominal size D mm

Hole

PositionGrade (IT)

Shaft

PositionGrade (IT)

Preferred fits (hole basis)

—

—µm—

Hole deviations

Upper deviation ES: —
Lower deviation EI: —
Maximum size: —
Minimum size: —
Tolerance: —

Shaft deviations

Upper deviation es: —
Lower deviation ei: —
Maximum size: —
Minimum size: —
Tolerance: —

Tolerance lookup

Type any class (e.g. H7, js6, N9, u6). Capitals are holes, lower case are shafts.

Tolerance class

Common classes at this size

Class	Upper dev. (µm)	Lower dev. (µm)	Max. (mm)	Min. (mm)

Formulae

E S = E I + I T_{n}

e s = e i + I T_{n}

C_{\max} = E S - e i

C_{\min} = E I - e s

Δ = I T_{n} - I T_{n - 1}

E S = - e i + Δ

A negative clearance is an interference. Cmin ≥ 0 is a clearance fit, Cmax ≤ 0 an interference fit, anything between a transition fit. The last formula gives the upper deviation of K, M, N holes (up to IT8) and P to U holes (up to IT7), where ei is the shaft fundamental deviation of the same letter.

Notes

Size ranges run "over a up to and including b": 30 mm falls in 18–30, 30.001 mm in 30–50.
JS and js classes are shown as exactly ±IT/2 (e.g. JS7 at Ø25: ±10.5 µm), as the ISO 286-2 tables print them.
K, M and N holes up to IT8, and P to U holes up to IT7, carry the correction Δ = ITn − IT(n−1). The ISO 286-1 special case applies: M6 at 250–315 mm has ES = −9 µm.
A fit can change type with size: H7/p6 is a transition fit up to 3 mm and an interference fit above.
Sizes apply at the 20 °C reference temperature of ISO 1. For interference fits, check separately whether assembly needs heating or cooling for the interference and the materials involved.

Sources (6)