How to use the print typography unit converter
- Enter a size and choose its unit from points, picas, Didot points, ciceros, Q, twips, millimeters, centimeters, inches or pixels.
- Read the headline size in millimeters and inches, and the key units in the results.
- Use the table to see the same size in every unit at once.
- Open the advanced options to change the pixels per inch or the Didot point size to match your source.
Formula
PostScript point = 25.4 / 72 mm (72 per inch)
US printer point = 25.4 / 72.27 mm (72.27 per inch)
Pica = 12 points; cicero = 12 Didot points
Q = 0.25 mm; twip = 1/1440 inch; inch = 25.4 mm
Didot point = 0.375972 mm as an editable example (27.07 mm / 72); pixel = 25.4 / pixels per inch mm
Every size is converted to millimeters first and then divided by the size of the target unit, so the conversions are consistent with each other.
Twelve points, one inch and 13 Q
12 PostScript points are exactly 1 pica and 4.2333 mm, or 0.1667 inches. In other units that is 12.045 US printer points, 11.2597 Didot points (with the example Didot size), 0.9383 ciceros, 16.9333 Q, 240 twips and 16 pixels at 96 per inch.
One inch is 72 PostScript points, 72.27 US printer points, 101.6 Q, 1,440 twips and 67.5582 Didot points. A type size of 13 Q is 3.25 mm, or 9.2126 PostScript points.
Why there are several kinds of point
The point has had many definitions over the centuries. Digital layout software settled on 72 points to the inch, called the PostScript or desktop publishing point. Traditional American and British printing used the printer's point, 72.27 to the inch, and TeX still does. Continental Europe used the Didot point, which is a little bigger, and the cicero of 12 Didot points. Japanese typesetting measures in Q, a quarter of a millimeter, so 13 Q is 3.25 mm.
The differences are tiny for one line but add up: a page set in US printer points and printed in PostScript points would be 0.4% off. Matching the system your tools use avoids small mismatches in line height and column depth.
Using the converter
Use the table to translate a specification written in one system for software that uses another, or to find the pixel size of a printed size at a given resolution. The Didot point has more than one accepted size, between about 0.3759 and 0.3761 mm, so it is an editable field: set it to the value your reference gives.
Related tools: the CSS unit converter for screen units, the paper size converter, the image DPI print size calculator, the type scale generator and the general unit converter.
Assumptions and limits
- The PostScript point is exactly 1/72 inch, the US printer point exactly 1/72.27 inch, and 1 inch is exactly 25.4 mm.
- The Didot point is an editable example of 0.375972 mm; definitions differ slightly between sources.
- Pixels depend on a resolution you choose; 96 per inch is the CSS reference density and not a property of every screen.
- Results are shown with up to 8 significant digits.
Frequently asked questions
What is the difference between a PostScript point and a printer's point?
The PostScript point is 1/72 inch and the printer's point is 1/72.27 inch. A 12-point line is 4.2333 mm in PostScript points and 4.2175 mm in printer's points, about 0.4% shorter.
What is a Q?
Q is a unit of 0.25 mm used in Japanese typesetting, especially for type sizes and character spacing. A 13 Q type size equals 3.25 mm, close to a 9.2 point PostScript size.
Why can the Didot point be edited?
Sources give slightly different values, from about 0.3759 to 0.3761 mm, depending on the era and country. Rather than pick one silently, the page lets you set the value your reference uses.
How many picas are in an inch?
Six, when using PostScript picas (72 points divided by 12). With US printer picas an inch is about 6.0225 picas, since an inch holds 72.27 printer points.