Typography Converter

Typography mixes physical and digital units, which is exactly why people end up converting between them. The point anchors print: one point is 1/72 of an inch, so 72 points make an inch and 12 points make a pica. Those are fixed physical sizes. Pixels are not.

Key conversions:

• 1 point (pt) = 0.35278 mm (1/72 inch)
• 1 pica = 4.2333 mm (12 points)
• 1 inch = 25.4 mm
• 1 pixel (at 96 dpi) = 0.26458 mm (1/96 inch)
• 1 em (at 16 px) = 4.2333 mm

Common sizes:

• Body text: 12 pt (about 16 px)
• Headings: 18–24 pt
• Small print: 8–9 pt

A pixel only has a physical size once you fix a resolution. The classic web assumption is 96 dpi, which is what the numbers above use, but a print file at 300 dpi or a phone screen near 460 dpi makes a pixel mean something entirely different. That’s why a layout that looks right on screen can print tiny if you treat pixels as a fixed length.

The em is the odd one out, because it isn’t an absolute size at all. One em equals the current font size, so 1 em is 16 px when the base text is 16 px, and it scales as the text scales. That relative behavior is precisely why em and rem are the preferred units in responsive web design, where everything has to grow and shrink together.

Resolutions worth knowing

Set the dpi in the converter above and every pixel figure moves with it. That is the whole point: a 16 px heading is 4.2 mm tall on the web and 1.4 mm on a 300 dpi print file, and treating the two as the same number is how a layout that looked fine on screen comes out of the printer unreadable.

em versus rem, since they convert identically

Both are relative to a font size, and the only difference is which font size. An em is relative to the element’s own size, so nesting compounds it: three levels of 0.9 em leaves you at 0.73 of where you started, which is the classic reason a deeply nested list ends up microscopic. A rem is always relative to the root element, so it never compounds. For conversion purposes they are the same unit and the numbers here apply to both; for authoring, reach for rem unless you specifically want the compounding.

Sizes people actually use

The 16 px web default is not arbitrary. It is what browsers have shipped for decades, and it is roughly the point at which body text stays comfortable at arm’s length on a desk. Setting a site’s body text below about 14 px is the single most common accessibility complaint, and it costs nothing to fix.