The ligne (pronounced [liɲ] ) 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] The loi du 19 frimaire an VIII (Law of 10 December 1799) states that one metre is equal to exactly 443.296 French lines.[4]

Unit systemFrench
Unit oflength
1 ligne in ...... is equal to ...
   French units   12 Truchet point
1/12 pouce
   metric (SI) units   2.2558 mm
   imperial/US units   0.08881 in

It is vestigially retained today by French and Swiss watchmakers to measure the size of watch movements,[5] in button making, and ribbon manufacture.

Current useEdit


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 of 0.0888 international inch.

This is comparable in size to the British measurement called "line" (one-twelfth of an English inch), used prior to 1824.[6]


In the 18th 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.[7][better source needed] It remains in US use today for buttons and snaps.[citation needed]


Ligne is used in measuring the width of ribbons in men's hat bands,[8] at 11.26 per inch.[9]

See alsoEdit


  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. JSTOR 1412884.
  2. ^ Stearn, W.T. (1992). Botanical Latin: History, grammar, syntax, terminology and vocabulary, Fourth edition. David and Charles.
  3. ^ Neumann, F. (January 1863). "IX. Experiments on the calorific conductibility of solids". Philosophical Magazine. 4. 25 (165): 63–65. doi:10.1080/14786446308643418.
  4. ^ Suzanne Débarbat. "Fixation de la longueur définitive du mètre" [Establishing the definitive metre] (in French). Ministère de la culture et de la communication (French ministry of culture and communications). Retrieved 2011-03-01.
  5. ^ Foire aux questions sur l'horlogerie et les montres [Frequently asked questions about watches and clocks] (in French),, retrieved 2010-06-30, Chaque ligne équivaut à 2,2558 mm, arrondis à 2,26 mm pour calculer plus rapidement. [Each line equals 2.2558 mm, rounded to 2.26 mm for faster calculation.]. (in French)
  6. ^ Oxford English Dictionary
  7. ^
  8. ^
  9. ^