readable-line-length

name	readable-line-length
description	Use when setting body text column width. 45-65 characters per line is optimal; 75+ causes reading fatigue.

Readable Line Length

Optimal reading line: 45-65 characters per line. Max: 75 characters. Below 45 = choppy; above 75 = lose-your-place fatigue.

Width caps by content type

Content	Width	Characters
Long-form article body	600-720px	60-75
News article body	540-660px	50-65
Marketing landing body	600-800px	60-80
Mobile body	100% (320-540px)	30-55
Caption	540px	50-65
List items	480-600px	45-60

Calculation

Characters per line = column width / character width Inter Tight 16pt: ~7.5px per character Fraunces 16pt: ~7.8px per character

600px ÷ 7.5 = 80 chars (slightly wide) 540px ÷ 7.5 = 72 chars (good)

Width caps in CSS

.body-prose {
  max-width: 70ch;  /* ch unit = approx 1 character */
  margin-inline: auto;
}

The ch unit (1 character-wide of the font) is the cleanest way to set readable column.

Where this fits in the X3 empire

Used as body width baseline across CardPrepAI editorial pages.