Counting or Casting off Copy (for both phrases are indifferently used) is to examine and find how much either of printed copy will come in into any intended number of sheets of a different body or measure from the copy; or how much written copy will make an intended number of sheets of any assigned body and measure. — M.
It is also used to ascertain how many sheets of a given sized page and letter any quantity of prepared copy will make.
This is generally done by composing a line or two of the copy, if it be manuscript, selected from the part that appears about the average mode of writing, and ascertaining how many lines of the printed or manuscript copy will make even lines in the proposed size; thus, if 10 lines of copy make 7 lines, or 7 lines of copy make 10 lines, the quantity is easily calculated. Allowance must of course be made for chapter heads, short pages, and any whites that may occur.