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1 ligne =
SI units
2.256×10^−3 m 2.2558 mm
US customary units (Imperial units)
7.401×10^−3 ft 88.81×10^−3 in
For the equivalent English unit, see Line (unit). For the Belgian tributary of the Sambre, see Ligne River.
Not to be confused with the French Line, a shipping company, or The French Line, a 1954 musical.

The ligne or line or Paris line,[1] is a historic unit of length used in France and elsewhere prior to the adoption of the metric system in the late 18th century, and used in various sciences after that time.[2][3] It is vestigially retained today by French and Swiss watchmakers to measure the size of watch movements,[4] in button making, and ribbon manufacture.



The ligne is still used by French and Swiss watchmakers

There are 12 lignes to one French inch (pouce). The standardized conversion for a ligne is 2.2558291 mm (1 mm = 0.443296 ligne), and it is abbreviated with the letter L or represented by the triple prime, ‴. One ligne is the equivalent 0.0888 inch.

This is comparable in size to the British measurement called "line" (one-twelfth of an English inch), used prior to 1824.[5]


In the 9th century German button makers began to use the term ligne to measure the diameter of buttons. The consensus definition was that a ligne was the measurement of a round wick, folded flat. In this sense it measures 140 of an inch, but not exactly, for there were several inches in the kingdoms and petty states of Germany at that time.

Such a measurement became the American measurement called "line," being one-fortieth of the US-customary inch, used measure buttons, probably introduced by German immigrants. It remains in US use today for buttons and snaps.[6]


Ligne is used in measuring the width of ribbons in men's hat bands,[7] at 11.26 per inch.[8]

See also[edit]


  1. ^ Gates, E.J. (1915). "The Determination of the Limens of Single and Dual Impression by the Method of Constant Stimuli". The American Journal of Psychology 26 (1): 152–157. doi:10.2307/1412884. 
  2. ^ Stearn, W.T. (1992). Botanical Latin: History, grammar, syntax, terminology and vocabulary, Fourth edition. David and Charles. 
  3. ^ Neumann, F. (1863). "IX. Experiments on the calorific conductibility of solids". Philosophical Magazine Series 4 25 (165): 63–65. doi:10.1080/14786446308643418. 
  4. ^ Foire aux questions sur l'horlogerie et les montres,, retrieved 2010-06-30 . (French)
  5. ^ Oxford English Dictionary
  6. ^
  7. ^
  8. ^