I have a paragraph of text:
Lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum
The latest way to go is to use the unit 'ch' which stands for character.
You can simply write:
p { max-width: 75ch; }
The only trick is that whitespaces won't be counted as characters..
Check also this post: https://stackoverflow.com/a/26975271/4069992