Source : Webster's Revised Unabridged Dictionary (1913)

Arithmetical \Ar`ith*met"ic*al\, a.
   Of or pertaining to arithmetic; according to the rules or
   method of arithmetic.

   {Arithmetical complement of a logarithm}. See {Logarithm}.

   {Arithmetical mean}. See {Mean}.

   {Arithmetical progression}. See {Progression}.

   {Arithmetical proportion}. See {Proportion}.

Source : WordNet®

arithmetical
     adj : relating to or involving arithmetic; "arithmetical
           computations" [syn: {arithmetic}]