Looking at different fragments of ancient and contemporary scrolls, I wondered
What are the considerations of determining the length of a line in Torah scroll/Chumash?
the Damascus Pentateuch
Contemporary Kosher Torah scroll
The standard ideal length of a line is about 30 letters long, enough to write למשפחותיכם thrice per line (Menachot 30a, YD 272:2). Lines that are too long are hard to follow and lines that are too short look like a note not a proper book. Some (Tosfot, etc.) say that the ~30 letter approximation can vary with the font size.