Ligne – Wikipedia

Unit of length

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]

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

Current use[edit]


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),[4] and it is abbreviated with the letter L or represented by the triple prime, .[5] 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] (The French inch at that time was slightly larger than the English one, but the system of 12 inches to a foot and 12 lines to an inch was the same in both cases.)


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

Button making[edit]

The button trade uses the term ligne (sometimes « line »), but with a substantially different definition: 140 inch (0.635 mm).[9][10]

See also[edit]

  1. ^ Par tradition ancestrale, les horlogers n’utilisent pas le millimètre mais la ligne pour désigner le diamètre d’encageage d’un mouvement.[5] [By ancestral tradition, watchmakers do not use the millimeter but the line to designate the casing diameter of a movement]


  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. ^ a b 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. ^ a b c « Foire aux questions sur l’horlogerie et les montres » [Frequently asked questions about watches and clocks], (in French), retrieved 2022-01-18
  6. ^ Oxford English Dictionary
  7. ^ « What are French Lignes? ».
  8. ^ « Converting between lignes and inches ».
  9. ^ « An Easy Guide to Button Measurement and Sizing ». Sun Mei Button Enterprise Co., Ltd. 2019-06-19.
  10. ^ The Metric System | Hearings Before a Subcommittee of the Committee on Manufactures, United States Senate, Sixty-seventh Congress, First and Second Sessions on S. 2267 a Bill to Fix the Metric System of Weights and Measures as the Single Standard of Weights and Measures for Certain Uses. By United States. Congress. Senate. Committee on Manufactures. October 11, 1921. p. 216.