Paragraph width

Paragraphs should be in between 50 and 70 characters of width¹. Too wide paragraphs will make readers take big horizontal movements when starting a new line. Too small paragraphs break the flow of reading text.

When working with CSS the ch unit can be used to achieve this. The ch unit is defined as:

“Equal to the used advance measure of the “0” (ZERO, U+0030) glyph found in the font used to render it.”

In proportional typefaces, 1ch is usually around 20% wider than the average character width². This makes the optimal paragraph width in CSS between 40ch and 60ch:

p {
    max-width: 55ch;
}

Fonts can however vary in their width. It is best to experiment width the value on each font to determine the best paragraph width.