You may want more evenly sized right margins than delivered by a greedy word wrap algorithm (filling as much as possible before breaking). cligen/textUt has this built into it (for help message formatting). It minimizes a penalty formula that is the sum of the p-th power of right margin space sizes. So this program is a razor thin CLI wrapper that is easy to use from, e.g. just :!ww from a vim visual select as I did for this very paragraph. Higher powers will penalize non-uniformity more.
ww [optional-params]
Multi-paragraph with indent=>pre-formatted optimal line wrapping using badness
metric sum excess space^power.
-h, --help print this cligen-erated help
--help-syntax advanced: prepend,plurals,..
-m=, --maxWidth= int 0 maximum line width; 0 => tty width
-p=, --power= int 3 power of excess space for badness
Donald Knuth did some impressive work in his TeX layout engine on the much harder problem that combines kerning adjustment of proportionally spaced fonts and word wrap. This program is the kind of high school version of that, but the concept of "badness" does still show up in tex/latex error messages and is in the same general dimension.