Width of Measures

Here's one way, for instance...
1. Create a score in, say, 4/4.
2. Enter nothing else but quarter notes.
The measures, all having the same number of notes, will have the same widths.

Since your music may be more interesting than that...
Please be more specific as to what your needs are, because measure width depends on musical content - i.e., a measure consisting of a run of 16th notes requires more width than another measure containing a single whole note.