Working a text width ceiling back into pixels
Choosing a max-width starts with the font size and how many characters a line should carry. Enter the body font size, the target character count, an average character width factor and the horizontal padding, and you get the text line width, the container width with padding included, and the same value in rem. The table covering your count plus or minus ten characters shows how far the width moves when the target shifts a little.
The formula is text width = characters times font size times the width factor, and the container width adds the total horizontal padding. The factor is average character width relative to font size, so it changes with the typeface: Latin body text sits near 0.5, while full-width scripts run higher, and measuring it in your own font is the accurate route. The CSS ch unit is the advance of the digit zero rather than an average character, so this page reports px and rem only. Values show two decimals and the code follows syntax current in October 2026.
The advice to keep lines between 45 and 75 characters is widely quoted, but the sources disagree and it is not a recognized standard. The target count is therefore an input and this page does not judge whether yours is appropriate. Evaluating the character count itself and email body width specifications belong to other tools, and line height, paragraph spacing and multi-column layouts are out of scope.
Frequently Asked Questions
Set a line of representative lowercase text in your font, divide its measured width by the number of characters, then divide again by the font size. Full-width scripts give a larger factor than Latin.
The widely quoted 45 to 75 range comes from sources that disagree, and it is not a recognized standard. The page takes your target as an input and does not judge it.
The ch unit measures the advance of the digit zero, which differs from an average character, so this page does not generate a ch value and reports px and rem instead.