What is the specific meaning of H7 in ISO tolerances?

In the ISO hole-basis system, H indicates a hole with zero lower deviation (EI = 0). The number 7 indicates the IT grade (IT7), which sets the tolerance width.

What is the difference between clearance and interference fit?

A clearance fit occurs when the minimum hole size is larger than the maximum shaft size. An interference fit occurs when the maximum shaft size is larger than the minimum hole size. Transition fits can be slightly either.

Which standard is used for this tolerance calculator?

This calculator follows ISO 286 limits and fits tables (IT grades and fundamental deviations) for linear sizes.

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ISO Tolerance Calculator (ISO 286) – Limits & Fits

Calculate hole tolerance and shaft tolerance, ISO limits, and clearance/interference (e.g. H7/h6). Includes an interactive fit diagram.

ISO Tolerance Calculator for Holes and Shafts (H7, h6, g6)

Use this tool as a tolerance calculator, ISO tolerance calculator, hole tolerance calculator, shaft tolerance calculator, and limits and fits calculator.

Inputs

Nominal size (mm)

Use dot “.” as decimal separator.

Output unit

Deviations are in µm; sizes are in mm.

Hole deviation

Hole IT grade

Shaft deviation

Shaft IT grade

Results

Fit designation

—

Fit type

—

Hole

Upper deviation (ES)

—

Lower deviation (EI)

—

Max size

—

Min size

—

Shaft

Upper deviation (es)

—

Lower deviation (ei)

—

Max size

—

Min size

—

Clearance / Interference

Maximum clearance/interference

—

Minimum clearance/interference

—

Fit diagram (relative to basic size)

Zero line Hole zone Shaft zone

Fit range Range in µm (negative = interference, positive = clearance).

How this ISO tolerance calculator works

Enter a nominal size (mm), pick a hole tolerance (e.g. H7) and a shaft tolerance (e.g. h6). The calculator looks up ISO 286 tolerance grades (IT) and fundamental deviations, then outputs limits and fit type.

Common searches

H7 tolerance calculator (hole basis fits like H7/h6)
Limits and fits calculator (clearance / transition / interference)
Hole tolerance calculator and shaft tolerance calculator

H7 Tolerance Calculator Explained

In the ISO hole-basis system, the letter H indicates a hole where the lower deviation is zero (EI = 0). The number (for example, 7 in H7) is the tolerance grade (IT7) which defines the tolerance width. The calculator retrieves the correct IT grade value and fundamental deviation from ISO lookup tables and computes limits of size.

Tip: H7/h6 is one of the most common preferred fits for general machining.

Example: 25 H7/h6 Fit

Enter Nominal size = 25, choose Hole = H7 and Shaft = h6. The calculator outputs hole and shaft limits and the resulting min/max clearance (or interference). The SVG diagram visualizes both tolerance zones relative to the zero line.

Example buttons prefill inputs; results update instantly.

Clearance, Transition and Interference Fits

Clearance fit: minimum hole size > maximum shaft size.
Interference fit: maximum shaft size > minimum hole size.
Transition fit: small clearance or small interference may occur depending on actual sizes.

ISO 286 Limits and Fits Standard

ISO 286 defines the code system of tolerances and fits for linear sizes using tolerance grades (IT) and fundamental deviations for hole and shaft positions. This calculator implements those tables to compute limits, fits and clearances.

Standards referenced

This page focuses on ISO 286 (metric limits and fits). For completeness, the broader limits-and-fits hub also covers related systems.

ISO 286-1 – Basis of tolerances, deviations and fits
ISO 286-2 – Tables of standard tolerance grades and limit deviations
ANSI/ASME B4.1 – Preferred limits and fits (inch)
ANSI/ASME B4.2 – Preferred metric limits and fits
ISO 2768 – General tolerances for dimensions without individual tolerance indications