Typographic points to Millimetres Converter

How it is calculated

Enter a size in typographic points. The tool uses the desktop-publishing point, defined as 1/72 of an inch: mm = points × 0.3527778 (which is 25.4 / 72) and inches = points / 72. Millimetres are shown with two decimals and inches with four.

This is the PostScript/DTP point used in design and layout programs, and in CSS where 1 pt is 1/72 of an inch. Older print traditions use slightly different points, such as the 1/72.27 inch printer's point (used by TeX) and the Didot point, so a result here can differ a little from a historical specification. Negative values are converted without complaint, which only makes sense for offsets. The tool converts the unit itself; it does not know the size of the font’s visible letters, which is smaller than the point size.

Common mistakes

• Thinking the point size is the height of a capital letter. It is the nominal body of the type, so the visible letters measure noticeably less than 4.23 mm at 12 pt.
• Mixing up points with pixels. In CSS a point is 1.333 pixels, so 12 pt is 16 px, and the two cannot be swapped one-for-one.
• Using the TeX printer's point (1/72.27 inch) or Didot point as if they were the DTP point. Their millimetre values differ slightly from this tool’s.
• Reading line spacing as type size. A 12 pt font with 14.4 pt leading takes 14.4 points of vertical space per line, which is about 5.08 mm.
• Rounding the factor by hand to 0.35. Over a large size such as 1,000 pt that already moves the answer by several millimetres.