AtlasCalcsUtility Calculation Suite
2026-07-30 8 min

Shaft Fit Calculator

Calculate shaft tolerances per ISO 286 standards.

Calculator

Unit System
Nominal Size (mm)
Shaft Type
IT Grade
Deviation Mode

Results

Normal

Tolerance (IT value)

27.3250mm

Total tolerance zone width

Upper Deviation (es)

0.0000mm

Upper deviation from nominal

Lower Deviation (ei)

-27.3250mm

Lower deviation from nominal

GO Diameter (MMC)

50.0000mm

Largest acceptable shaft diameter

NO-GO Diameter (LMC)

22.6750mm

Smallest acceptable shaft diameter

Fit Type

Clearance

Type of fit

Tolerance Unit (i)

1.708mm

Standard tolerance unit i

Visualizations

Results Overview

27.3mmTolerance
50mmGO Diameter
22.7mmNO-GO Diameter
1.7mmTolerance Unit

Formula

ISO 286 defines shaft tolerances using the shaft basis system with h as reference.

i = 0.45xcbrt(D) + 0.001xD, IT7 = 16xi, es = deviation table, ei = es - ITn

Alternative Form

For h7: es = 0, ei = -IT7

Variables

SymbolNameUnitDescription
DGeometric MeanmmGeometric mean of diameter range limits
iTolerance UnitmmStandard tolerance unit per ISO 286
ITnIT GrademmTolerance for the specified IT grade
eiLower DeviationmmLower deviation (external features)
esUpper DeviationmmUpper deviation (external features)

Explanation

ISO 286 provides a systematic framework for shaft tolerances. The shaft basis uses h as reference with zero upper deviation.

Derivation

Tolerance unit i = 0.45 x cbrt(D) + 0.001 x D from empirical manufacturing data.

Step-by-Step Calculation

Follow each step to understand how the result is calculated from your inputs.

Step 1

Calculate geometric mean.

Nominal Size:50.0000 mm
Result: D = 50.000 mm
Step 2

Compute tolerance unit i.

i = 0.45 x cbrt(D) + 0.001 x D
D:50.000 mm
Result: i = 1.708 mm
Step 3

Apply IT grade and deviation.

ITn = multiplier x i, es = deviation table
IT Grade:IT7
Type:h
Intermediate: es = 0.0000 mm, ei = -27.3250 mm
Result: GO = 50.0000 mm, NO-GO = 22.6750 mm
Final Answer
27.3250

Worked Examples

See how the calculator works with different scenarios.

Scenario

50 mm shaft with h7 tolerance.

Inputs

Nominal:50 mm
Type:h
Grade:IT7

Calculation

IT7 = 16 x 1.78 = 28.4 um

Result

Upper Dev = 0, Lower Dev = -0.028 mm, GO = 50.000, NO-GO = 49.972

Interpretation

h7 is shaft-basis reference. Shaft is slightly smaller than nominal.

Understanding Your Result

Your Result: Tolerance (IT value): 27.3250 mm

Typical range: h6/g6/f6: Clearance. k6/m6/n6: Transition. p6/r6/s6/t6/u6: Interference.

What This Means

Shaft tolerance per ISO 286 defines acceptable shaft diameters. Letters a-h: clearance, js-n: transition, p-u: interference.

Why It Matters

Correct shaft tolerance ensures proper assembly. Shaft-basis is preferred for standard shafting.

Professional Interpretation

h6 for shaft-basis. g6 for running fits. p6 for press fits.

Recommendations

  • •Use h6 for shaft-basis precision designs
  • •Select g6 for precision running fits with H7 holes
  • •Use f7 for free-running fits with lubrication
  • •Apply k6/m6 for transition fits
  • •Select p6/s6 for press fits requiring interference

Educational Content

Introduction

ISO 286 defines limits and fits. Shaft letters a-h: clearance, js-n: transition, p-u: interference.

Concept Explanation

Shaft tolerances are defined by a letter (fundamental deviation) and IT grade number.

Applications

▸Rotating shaft bearings
▸Linear motion shafts
▸Piston assemblies
▸Gear mounting
▸Valve stems

Benefits

  • •Systematic tolerance selection
  • •International standardization
  • •Clearance/transition/interference fits

Limitations

  • •No geometric tolerances
  • •May not suit all materials
  • •No thermal effects

Best Practices

  • •Use shaft-basis with standard shafting
  • •Clearance fits for rotating shafts
  • •Interference fits for permanent assemblies

Common Misconceptions

Myth: Shaft-basis is always preferred.
Truth: Hole-basis is more common (80% of applications).
Myth: Tighter tolerance = better fit.
Truth: Use the loosest acceptable fit for function.
Myth: Shaft tolerances are symmetrical.
Truth: Only js provides symmetrical tolerance.

Practical Tips

  • •Use h6/g6 with H7 holes
  • •p6 for light press, s6 for heavy press
  • •Document fits as H7/g6

Common Mistakes

Interference fit for disassembly-needed parts
Use transition fits (k, m, n).
Confusing es and ei
es is always larger (closer to +infinity).
Ignoring surface finish
Ra 0.4-0.8 um for tight fits.

Assumptions

This calculator makes the following assumptions to provide estimates:

ISO 286 Defaults: Deviations per ISO 286 standard formulas.
Temperature at 20C: Reference temperature per ISO 1.
Cylindrical Features: Assumes round cylindrical shafts.

Limitations

Be aware of these limitations when using this calculator:

Simplified Tables: Uses approximate formulas. Consult ISO 286 for exact values.
No Geometric Tolerance: Size tolerance only. Geometric per ISO 1101.
Limited Types: Common shaft types implemented.

Frequently Asked Questions

Answers to common questions about this calculator.

What is shaft basis?
Fixes shaft tolerance (h) and varies hole tolerance for different fits.
What does h7 mean?
Zero upper deviation (es=0) with IT7 grade.
Difference between h6 and g6?
h6: es=0. g6: es negative (below nominal).
Most common clearance fit?
H7/g6 for precision rotating shafts.
Most common press fit?
H7/p6 light press. H7/s6 heavy press.
How is es calculated?
Clearance shafts (a-h): negative es. Interference (p-u): positive es.
What is tolerance unit i?
i = 0.45 x cbrt(D) + 0.001 x D.
Which types give clearance?
a, b, c, d, e, f, g, h with H holes.
Which types give transition?
js, k, m, n.
Which types give interference?
p, r, s, t, u.
What standard applies?
ISO 286 (international). ASME B4.1 (American).
How is fit tolerance calculated?
Fit tol = hole tol + shaft tol.
Shaft vs hole letters?
Shaft: lowercase. Hole: uppercase.
GO gauge for shaft?
Checks max diameter (MMC). Should fit over shaft.
NO-GO gauge for shaft?
Checks min diameter (LMC). Should NOT fit.
Shaft tolerance for bearings?
j5/k5 for rotating. h5/g5 for non-rotating.
Fit for sliding shaft?
H7/f7 standard. H7/g6 precise.
Clearance vs interference?
Clearance: shaft < hole. Interference: shaft > hole.
Temperature effect?
Steel ~12 um/m/C. 50 mm at 80C is ~36 um larger.
Thermal fit calculation?
Expansion = alpha x D x deltaT. Steel alpha=12x10^-6/C.
Mix hole and shaft basis?
Possible but consistency recommended.
Keyed connection fit?
H7/k6 transition fit for shaft-to-hub.
Surface finish effect?
Reduces effective diameter by ~4x Ra.
h5 vs h6?
h5 (IT5=7xi) tighter than h6 (IT6=10xi).
Seal running surface?
h8/h9 with 0.2-0.4 um Ra finish.
Specify on drawing?
50h7 or 50H7/g6 for assembly.
Renard series?
R5/R10: 7, 10, 16, 25, 40, 64, 100, 160, 250, 400, 640, 1000.
Measurement equipment?
Micrometers, snap gauges, bench micrometers, CMMs.
Material effect?
Harder materials hold tighter tolerances.
Cost impact?
IT5-IT6 may need grinding, cost 50-150% more than IT7-IT8.

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Related Guides

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Glossary

Technical terms used in mortgage calculations explained in plain language.

ei
Lower deviation of shaft - min limit minus nominal.
es
Upper deviation of shaft - max limit minus nominal.
IT Grade
International Tolerance grade per ISO 286.
Fundamental Deviation
Deviation closest to nominal. For shafts, usually es.
Shaft Basis
Shaft tolerance fixed (h), hole tolerance varied.
Clearance Fit
Shaft always smaller than hole.
Transition Fit
Shaft may be slightly larger or smaller.
Interference Fit
Shaft always larger than hole.
GO Gauge
Snap/ring gauge checking max shaft diameter.
NO-GO Gauge
Snap/ring gauge checking min shaft diameter.

Authoritative References

Trusted sources and standards referenced by this calculator.

Applicable Standards

ISO 286ISO 2768ASME B4.1ISO 1101ISO 8015ISO 5459

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Page Information

Last Updated:

2026-07-30

Version:

2.0.0

License:

Free to use for educational and professional purposes.