ConverterHub

Cicero to Millimeter Converter

Enter a value and direction to convert ciceros and millimeters.

Result

189.4746 mm
1 cicero = 4.5113 mm
504.00 Didot points

How it is calculated

The tool uses one fixed factor, 1 cicero = 4.5113 mm, and the Didot relation 1 cicero = 12 Didot points. Cicero to millimetre: mm = cicero × 4.5113. Millimetre to cicero: cicero = mm ÷ 4.5113. In both directions it also reports the length in Didot points (points = cicero × 12). Millimetre and cicero results are shown to four decimals, points to two. A negative or empty value returns no result, zero is accepted and gives zero, and any direction other than millimetre-to-cicero is treated as cicero-to-millimetre. The factor is the Didot one, not the Anglo-American pica.

Worked example

A typesetter specifies a text column that is 42 ciceros wide. Step 1: take the factor 4.5113 mm per cicero. Step 2: 42 × 4.5113 = 189.4746 mm. Step 3: the points figure is 42 × 12 = 504, shown as 504.00 Didot points. The result is 189.4746 mm, or about 19 cm. In the reverse direction, 100 mm gives 22.1666 cicero, which is 266.00 Didot points.

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Common mistakes

  • Using the Anglo-American pica (about 4.2175 mm) or a 72.27-per-inch point for a Didot specification. The two systems differ by roughly 7%, which adds up quickly over a full page.
  • Leaving the direction on cicero-to-millimetre when the number you have is already in millimetres, so the result is about 4.5 times too large.
  • Confusing ciceros with Didot points: 12 points make one cicero, so a 10 point type size is not 10 ciceros.
  • Rounding the factor to 4.5 mm; on a 42 cicero column that already shifts the width by about half a millimetre.
  • Entering a negative value to mean an offset or overhang. The tool only accepts zero or positive lengths and shows no result otherwise.

About this calculator

The cicero is the base unit of the Didot point system, the typographic measurement standard developed in 18th-century France and still used across much of continental Europe: 1 cicero equals 12 Didot points, which works out to 4.5113 mm — distinct from the Anglo-American pica/point system (based on 72.27 points per inch) used in the US and UK.

European typesetters, print designers, and typography historians use cicero-to-millimeter conversions when working with older European typefaces, historical printing specifications, or software and type foundries that still specify sizes in ciceros and Didot points rather than the point sizes common in English-language desktop publishing.

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