Typographic Units Converter (Points, Picas, Didot, Pixels)

There are at least four different points in print and they are up to 7% apart: the PostScript point your software means by “pt”, the TeX or American printer’s point, and the Didot point of continental Europe, whose own value is genuinely disputed. This converts between all of them, with picas, ciceros, agates, twips, millimetres, inches and CSS pixels.

Four points, one millimetre

Everything called a point, and what it actually measures

Common type sizes in each point, to the micrometre

The derived units, and what each is for

Four points, and the 7% between them

A point is not a unit, it is a family of arguments. When your software says “12 pt” it means the PostScript point: exactly 1/72 of an inch, which is exactly 0.352778 mm. Adobe put that definition into PostScript in 1984, CSS adopted it, and it is now what everybody means in practice. But TeX means something else — the American printer’s point of 1886, 1/72.27 in, 0.351460 mm — and it is 0.375% smaller. And continental European type has always been specified in Didot points, which are about 6.6% larger than PostScript points. The full spread, TeX point to Berthold Didot, is 7.00%.

The Didot point is the one that is genuinely unsettled. François-Ambroise Didot defined it in 1783 as 1/72 of a French inch, which works out at 0.375972 mm. Berthold redefined it in 1878 as 798 points to 30 cm, or equivalently 2,660 to the metre — 0.375940 mm. DIN 16507 gives 0.376065 mm, which is the figure most foundries and most software used, and TeX’s dd unit uses it too. And the “metric Didot”, DIN’s nominal value and TeX’s nd, is 0.375 mm exactly. Those four are 0.28% apart. This page carries all four separately and labels each, because averaging them would invent a length no printer ever set type in — and because a document that names its own Didot value should be converted on that value and not on a consensus.

The derived units inherit the argument. A pica is twelve points, so there are two picas: the ordinary one at 1/6 in exactly, and the TeX pica at 0.166044 in — Nelson Hawks and Lawrence Johnson’s pica, the one the 72.27 comes from. A cicero is twelve Didot points, 4.513 mm on Berthold’s value and 4.500 on the metric one, and it is the continental equivalent of a pica. An agate is 5.5 points, a newspaper classified measure that puts 13.09 lines in an inch — the widely repeated “fourteen agate lines to the inch” is a different and incompatible claim, and it would make an agate 5.143 points. A twip is a twentieth of a point, 1/1440 in, 17.64 µm; it exists so word processors can hold positions in integers, which is why RTF files are full of multiples of 1,440.

And the CSS pixel, which is now a typographic unit whether anyone likes it or not. The CSS specification defines an inch as exactly 96 px, so a CSS pixel is 1/96 in and a CSS point is exactly 4/3 of a CSS pixel. None of that is a claim about your screen: it is a reference frame, and a browser on a high-density display renders more physical dots per CSS pixel so that 16 px type stays the same apparent size. That is why 12 pt type in a browser is 16 px, and why designers who move between print and web find the two systems line up exactly at the ratio 4:3.

What this page is for. Taking a measurement off a European specification sheet and putting it into a modern application without being 6% out, and working out which point your software means before you argue with someone about it. For the relative units the same browsers use — em, rem and percentages — see the em, rem and px converter, and for the sheet a page box is measured against, the paper size converter, which gives every ISO size in points as well as millimetres.

Frequently asked questions

Related calculators

References

1. Wikipedia, Point (typography) (read 26 September 2026), for the competing definitions and their dates: the Didot point of 1783 at 1/72 of a French inch, “approximately 0.375972 mm”; Berthold’s 1878 redefinition, “0.376065 mm”, with 798 points to 30 cm; the DIN nominal value of 0.375 mm; the American point of 1886 at 0.013837 in, on a Johnson pica of 0.166044 in; the TeX point of 1982 at 1/72.27 in = 0.35145980 mm; and the PostScript point of 1984 at 1/72 in.
2. Wikipedia, Agate (typography) (read 26 September 2026): an agate is 5.5 points, and “a little over thirteen lines go to the inch”. The common claim that there are fourteen agate lines to the inch would make an agate 5.143 points, 6.7% smaller; the thirteen-and-a-bit figure is the one consistent with 5.5 points and is what this page uses.
3. Wikipedia, Twip (read 26 September 2026): “a twip … is defined as 1/20 of a typographical point. One twip is 1/1440 inch, or 17.64 μm”, used by Rich Text Format, LibreOffice, Visual Basic 6 and Symbian.
4. W3C, CSS Values and Units Module Level 4 (w3.org/TR/css-values-4/ and the editor’s draft at drafts.csswg.org, read 26 September 2026) — a public specification, quoted directly. It fixes 1in = 96px, 1pt = 1/72in, 1pc = 12pt and 1px = 1/96in; defines em as “the computed value of the font-size property of the element on which it is used”, and notes that in the font-size property itself it resolves against the size inherited from the parent; defines rem as “the computed value of the em unit on the root element”; and defines ex as the used x-height and ch as the advance measure of the “0” glyph — both font metrics, which is why this page refuses them. It also gives the fallbacks the spec mandates when those metrics are unavailable: “a value of 0.5em must be assumed” for ex.
5. National Institute of Standards and Technology, Refinement of Values for the Yard and the Pound, Federal Register notice of 1 July 1959, which fixed the international inch at exactly 25.4 mm and the avoirdupois pound at exactly 0.45359237 kg. Both exact values are used throughout this batch; every inch-to-millimetre figure here is therefore exact, not approximate.