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Tolerance is the permissible limit of variation in dimension.

Allowance is a concept very similar to tolerance but is different in the sense that allowance refers to tolerance in dimension that is deliberately given to a metal during the process of manufacture and design. This is a planned deviation from the standard that is intended to allow for compensation should there be any unforeseen circumstances that interfere with the dimensions of the metal parts or components.

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  • The difference between the upper limit and lower limit is called tolerance.
  • It is impossible to make any part to exact size.when working to a high degree of accuracy condition,
  • The amount of error that can be tolerated can be is represented by limits on the drawing.
  • Tolerance is the limit of random(unintentional) deviation of a dimensions from nominal values.
  • Metal parts are used in many numbers in assembles and manufacturing industries.These parts must have to fit each other with comfortably.
  • In the assembly metal parts need to have tolerance that allows compress.
  • The limit of tolerance of a metal is based on the metal properties.


  • Allowance is calculated as the difference between the maximum shaft size and minimum hole size is known as allowance.
  • It is a amount of designed (intentional) deviation between two mating parts of dimensions in a fit.
  • In a clearance fit it is have a minimum clearance and is positive allowance.
  • In an interference fit it is have a maximum interference and is negative allowance.
  • Allowance is the difference between the dimensions of hole and shaft.

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Allowance is the difference between the basic size of two mating parts; it could be positive or negative. For instance; if shaft size is less than the hole size, It is called positive allowance and in negative allowance, shaft size is greater than the hole size. On the other hand, tolerance is the difference between the maximum and minimum limit of the size or it is the maximum permissible variation of size.

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