Posted by flywire on Jun 26, 2020; 11:35am
URL: https://forum.librecad.org/Can-I-define-distances-between-points-in-Librecad-2-1-3-tp5719156p5719172.html

Have a look at https://dokuwiki.librecad.org/doku.php/usage:tutorials - Measure areas on a map, Solution 2: Rescale your image.

Otherwise do it in Gimp (or whatever package you are using).