Internal`GetIteratorLength

Internal`GetIteratorLength[it] returns the length (= number of iterations to be performed) of a standard iterator it such as is used in Table.

Internal`GetIteratorLength[{x, 3, 10}]
(*  8  *)

Internal`GetIteratorLength[{x, 3, 10, 0.27}]
(*  26  *)

Internal`GetIteratorLength[{x, {3, 4, 7}}]
(*  3  *)

Internal`GetIteratorLength[{4}]
(*  4  *)