Skip to main content
Machinist Free Pro Features Available

Tolerance & Fit Calculator — ISO 286 Shaft & Hole Fits with Visual Tolerance Zones

Clearance, Transition, and Interference Fits with Common Presets, Deviation Tables, and Tolerance Zone Diagrams

Free ISO 286 tolerance and fit calculator for mechanical engineers, machinists, and toolmakers. Enter a nominal size and select hole and shaft tolerance grades (e.g., H7/g6, H7/h6, H7/p6) to calculate upper and lower deviations, tolerance zones, maximum and minimum clearance or interference, and fit type. Includes a visual tolerance zone diagram showing the shaft and hole ranges relative to nominal. Preset fits for clearance (running, sliding, locational), transition (push, wringing), and interference (press, shrink) are built in for quick selection.

Pro Tip: In a production shop, the most commonly used fit by far is H7/g6 for precision sliding fits (bearings, guide pins, pistons). If you're not sure what fit to specify, start with H7/g6 for parts that need to slide with minimal play, or H7/p6 for parts that need to stay put without a key or setscrew. The "H" basis (hole basis) system is almost always preferred because standard reamers cut H7 holes and you adjust the shaft to fit. Shaft-basis fits (using h shafts) require custom hole sizes and are rarely used outside of specific bearing applications.

Check press fit and clearance for bearing installations

Press Fit Clearance Checker →

Calculate bearing life with proper shaft tolerances

Bearing Life Calculator →

Read the ISO tolerance and fit guide

ISO Tolerance & Fit Guide →

Convert between hardness scales for material selection

Hardness Converter →

PREVIEW All Pro features are currently free for a limited time. No license key required.

Tolerance & Fit Calculator
Pop Out

How It Works

  1. Enter Nominal Size

    Input the nominal (basic) dimension in millimeters. This is the design size before tolerances are applied. The calculator supports sizes from 1mm to 500mm per ISO 286 standard tables.

  2. Select Hole Tolerance

    Choose the hole tolerance designation. The letter indicates the fundamental deviation (position of the tolerance zone relative to nominal), and the number indicates the IT grade (width of the tolerance zone). H7 is the most common hole tolerance — the lower deviation is zero (hole is at or above nominal).

  3. Select Shaft Tolerance

    Choose the shaft tolerance designation. Letters a-h produce clearance fits (shaft smaller than hole), j-n produce transition fits, and p-z produce interference fits (shaft larger than hole). Common selections include g6, h6, k6, p6, and s6.

  4. Use Presets (Optional)

    Select from common fit presets: H7/g6 (close running), H7/h6 (sliding), H7/k6 (locational transition), H7/p6 (locational interference), or H7/s6 (medium press). The preset auto-fills both hole and shaft selections.

  5. Review Results

    See the upper and lower limits for both hole and shaft, maximum and minimum clearance (or interference), fit type classification, and a visual tolerance zone diagram. The diagram shows the relative positions and widths of both tolerance zones against the nominal dimension so you can visualize the fit at a glance.

Built For

  • Mechanical engineers specifying hole and shaft tolerances on engineering drawings per ISO 286 standards
  • Machinists determining actual size limits to machine a shaft to achieve an H7/g6 sliding fit in a bore
  • Toolmakers designing fixture components with precision fits for guide pins, dowels, and bushings
  • Maintenance technicians verifying whether a worn shaft still falls within the tolerance zone for its intended fit
  • Students and apprentices learning the ISO tolerance system and the relationship between deviation, grade, and fit type
  • Quality inspectors checking incoming parts against specified tolerance grades using go/no-go gauges

Features & Capabilities

ISO 286 Deviation Tables

Full fundamental deviation tables for hole positions A through ZC and shaft positions a through zc, covering IT grades 01 through 18. All values are calculated per ISO 286-1:2010 standard formulas and verified against published tables.

Visual Tolerance Zone Diagram

An interactive diagram shows the hole and shaft tolerance zones as colored bands relative to the nominal dimension. Clearance appears as a gap between bands, interference as an overlap. The diagram updates in real time as you change selections.

Common Fit Presets

One-click presets for the most commonly specified fits: H11/c11 (loose running), H9/d9 (free running), H8/f7 (close running), H7/g6 (sliding), H7/h6 (locational clearance), H7/k6 (locational transition), H7/n6 (locational interference), H7/p6 (press), and H7/s6 (heavy press). Each preset includes a description of its typical application.

Max/Min Clearance and Interference

Calculates the maximum clearance, minimum clearance, maximum interference, and minimum interference for the selected fit. For transition fits where the result can be either clearance or interference, both values are shown with the probability of each condition.

Fit Type Classification

Automatically classifies the fit as clearance, transition, or interference based on the calculated limits. Includes the specific fit category (running, sliding, locational, press, shrink) and the typical applications for that fit type.

Inch/Metric Support

Primary calculations are in metric per ISO 286. Results can be displayed in both millimeters and inches for shops that work in imperial. Nominal size input accepts either unit with automatic conversion.

Assumptions

  • Fundamental deviations and IT grades per ISO 286-1:2010 (metric) and ANSI/ASME B4.2 (inch equivalent)
  • Hole-basis system (H holes) assumed as default unless user selects shaft-basis fits
  • Tolerance zone calculations assume nominal size at 20 degrees C (68 degrees F) reference temperature per ISO 1
  • Maximum and minimum clearance/interference calculated from worst-case combinations of hole and shaft limits
  • Fit type classification (clearance, transition, interference) determined by overlap of tolerance zones
  • Standard IT grades IT5 through IT11 available; IT01 through IT4 and IT12+ require specialized manufacturing

Limitations

  • Does not account for thermal expansion that changes effective fit at operating temperatures above or below 20 degrees C
  • Surface finish effects on functional fit not modeled; rough surfaces reduce effective clearance
  • Does not calculate press fit assembly force, extraction force, or holding torque for interference fits
  • Elastic deformation of thin-walled parts under interference fit not considered in the tolerance zone model
  • Geometric tolerances (roundness, cylindricity, straightness) that affect real fit behavior are not included
  • Plating and coating thickness changes effective dimensions and must be accounted for separately

References

  • ISO 286-1:2010 - Geometrical Product Specifications (GPS) — ISO Code System for Tolerances on Linear Sizes
  • ISO 286-2:2010 - Tables of Standard Tolerance Classes and Limit Deviations for Holes and Shafts
  • ANSI/ASME B4.2 - Preferred Metric Limits and Fits (American adoption of ISO 286)
  • ASME B4.1 - Preferred Limits and Fits for Cylindrical Parts (inch-based RC, LC, LT, LN, FN fits)
  • Machinery's Handbook, 31st Edition - Tolerance, Allowance, and Preferred Fits Tables
  • ISO 1 - Geometrical Product Specifications — Standard Reference Temperature for Product Specification

Frequently Asked Questions

A clearance fit always has a gap between the shaft and hole — the shaft is always smaller than the hole. A transition fit may have either a slight clearance or a slight interference depending on where in the tolerance zones the actual parts fall. An interference fit always has overlap — the shaft is always larger than the hole and must be pressed or shrink-fitted. Clearance fits allow free movement, transition fits locate parts precisely, and interference fits hold parts together by friction.
The H designation means the fundamental deviation is zero, so the hole is at nominal on the small end and larger by the IT7 tolerance on the large end. This simplifies manufacturing because H7 holes can be made with standard reamers that are ground to the nominal size. You then adjust the shaft diameter to achieve the desired fit. This is called the hole-basis system and is preferred in nearly all industries because reamers are expensive, while turning a shaft to a specific diameter is routine.
IT grades range from IT01 (tightest, used for gauge blocks) to IT18 (loosest, used for structural steel). For precision fits involving bearings, guide pins, and machine tool components, IT6-IT7 is standard. For general mechanical components, IT8-IT9 is adequate. For rough fits and structural work, IT11-IT12 is common. Tighter grades cost more to manufacture because they require finishing operations (grinding, honing, lapping) rather than just turning or milling.
H7/p6 is a light press fit where assembly can be done with an arbor press at room temperature. The interference is small enough that parts can be disassembled without damage. H7/s6 is a medium-to-heavy press fit that typically requires heating the hole or cooling the shaft for assembly. It provides significantly more holding force but is essentially permanent. Use p6 for components that may need replacement (bearings, bushings) and s6 for permanent assemblies (gear hubs, flywheel bores).
ISO 286 is inherently a metric standard. The tolerance zones, fundamental deviations, and IT grades are defined in millimeters. However, the ANSI/ASME B4.2 standard provides the equivalent tolerance system for inch dimensions using the same letter-number designations. This calculator works natively in metric and converts to inches for display. For pure inch-based work, the ANSI fit classes (RC, LC, LT, LN, FN) are the traditional American equivalent.
Disclaimer: Tolerance calculations are based on ISO 286-1:2010 standard tables and formulas. Actual fit behavior depends on surface finish, material properties, lubrication, temperature, and manufacturing process. Critical fits should be verified by test assembly or inspection with calibrated instruments. ToolGrit is not responsible for fit failures or assembly problems resulting from calculator use.

Learn More

Machinist

ISO 286 Tolerance & Fit Guide: How to Select Shaft/Hole Fits for Machining

Practical guide to ISO 286 tolerance zones and fits. Covers clearance, transition, and interference fits with real-world examples. Includes common fit selections (H7/g6, H7/h6, H7/p6) and when to use each.

Read Guide →
Machinist

GD&T Symbols Explained: A Practical Guide for Machinists

All 14 geometric tolerance symbols per ASME Y14.5 explained in plain English. When to use each, what they control, and how they are inspected.

Read Guide →

Related Tools

Machinist Live

Chip Load Calculator

Calculate chip load per tooth for milling, drilling, and turning. Forward and reverse modes with material-specific recommendations, chip thinning factor, and MRR. Metal and wood modes.

Launch Tool →
Machinist Live

Thread Pitch Identifier

Identify unknown threads from caliper measurements. Cross-references UNC, UNF, Metric ISO, NPT, BSP, and ACME thread standards with tolerance matching and confidence scoring.

Launch Tool →
Machinist Live

Material Weight Calculator

Calculate weight of metal stock in 9 shapes: round bar, tube, square, hex, sheet, angle iron, and more. 16 materials with cut list builder and cost estimator.

Launch Tool →