Running the regular expression search:
. . . in a text editor like NotePad++ will generate a count of the number of non-empty lines in a text file. The number of hits will be shown in the results pane below the transcript.
In order to get a count of the number of empty lines you can run this RegEx search: ^\s*$
. . . but note that it will count consecutive lines with only whitespace as a single line.