Preferred metric fits and tolerances for hole and shaft basis systems which are given in ISO 286-1 (2010) and ANSI B4.2-1978 standards are summarized in the following tables. The usage of these tolerances is advised for economic reasons.

Supplement: Preferred fits advised by ISO and ANSI standards

Preferred fits table (ANSI B4.2-1978)

  ISO Symbol Description
Hole Basis Shaft Basis
Clearance Fits H11/c11 C11/h11 Loose running fit for wide commercial tolerances or allowances on external members.
H9/d9 D9/h9 Free running fit not for use where accuracy is essential, but good for large temperature variations, high running speeds, or heavy journal pressures.
H8/f7 F8/h7 Close running fit for running on accurate machines and for accurate location at moderate speeds and journal pressures.
H7/g6 G7/h6 Sliding fit not intended to run freely, but to move and turn freely and locate accurately.
H7/h6 H7/h6 Locational clearance fit provides snug fit for locating stationary parts; but can be freely assembled and disassembled.
Transition Fits H7/k6 K7/h6 Locational transition fit for accurate location, a compromise between clearance and interference.
H7/n6 N7/h6 Locational transition fit for more accurate location where greater interference is permissible.
Interference Fits H7/p6 P7/h6 Locational interference fit for parts requiring rigidity and alignment with prime accuracy of location but without special bore pressure requirements.
H7/s6 S7/h6 Medium drive fit for ordinary steel parts or shrink fits on light sections, the tightest fit usable with cast iron.
H7/u6 U7/h6 Force fit suitable for parts which can be highly stressed or for shrink fits where the heavy pressing forces required are impractical.
Tolerance classes for shafts
Clearance Fits Transition Fits Interference Fits
H6           g5 h5 js5 k5 m5   n5 p5          
H7         f6  g6 h6 js6 k6 m6 n6   p6 r6 s6 t6 u6 x6
H8       e7 f7   h7 js7 k7 m7         s7   u7  
    d8 e8 f8   h8                      
H9     d8 e8 f8   h8                      
H10 b9 c9 d9 e9     h9                      
H11 b11 c11 d10       h10                      

Preferable fits of the hole-basis system (ISO 286-1:2010)

Tolerance classes for holes
Clearance Fits Transition Fits Interference Fits
h5           G6 H6 JS6 K6 M6   N6 P6          
h6         F7 G7 H7 JS7 K7 M7 N7   P7 R7 S7 T7 U7 X7
h7       E8 F8   H8                      
h8     D9 E9 F9   H9                      
h9       E8 F8   H8                      
    D9 E9 F9   H9                      
B11 C10 D10       H10                      

Preferable fits of the shaft-basis system (ISO 286-1:2010)

Note: For economic reasons, the first choice for a fit should, whenever possible, be made from the tolerance classes shown with green color.


Link Usage
Limits, fits and tolerance calculator Designed to calculate the limits, fits and tolerances according to ISO 286(2010) and ANSI B4.2 (1978) standards.


  • Oberg, E. , Jones ,F.D. , Horton H.L. , Ryffel H.H., (2016) . Machinery's Handbook . 30th edition.  Industrial Press Inc.
  • Oberg, E. , Jones ,F.D. , Horton H.L. , Ryffel H.H., (2012) . Machinery's Handbook . 29th edition.  Industrial Press Inc.
  • IS0 286-1 (2010) Geometrical product specifications (GPS) - ISO code system for tolerances on linear sizes - Part 1: Basis of tolerances, deviations and fits
  • IS0 286-2 (2010) Geometrical product specifications (GPS) - ISO code system for tolerances on linear sizes - Part 2: Tables of standard tolerance classes and limit deviations for holes and shafts
  • ANSI/ASME B4.2 (1978) Preferred Metric Limits and Fits