ligne

A ligne is a unit of linear measurement equal to one twelfth of a pouce (French inch), or approximately 2.256 millimetres. In textile and garment production, it serves as the standard measure for button diameter, particularly in European manufacturing. A button marked as 20 lignes, for example, measures roughly 45 millimetres across.

The ligne persists as a working standard despite metrication because button sizes have long been specified and manufactured in this unit. Thread counts, shank heights, and hole spacing on buttons are still often given in lignes across French, Italian, and German mills. Most plastic and metal button catalogues maintain both metric and ligne specifications, with common sizes clustering around 12, 14, 16, 18, 20, 24, and 28 lignes for apparel applications.

Historical roots and modern use

The ligne derives from the pied du roi, the pre-metric French measurement system. Although the metre became official in 1793, the ligne remained entrenched in button manufacturing because button blanks and tooling were already calibrated to these dimensions. Replacing production dies and gauging equipment would have been costly, so the unit was simply carried forward into the industrial era and remains there.

A garment technician sourcing buttons from European suppliers will encounter ligne specifications on specification sheets and in order codes. The measurement is taken across the button face (the widest diameter for domed or shank buttons). Tolerance is typically plus or minus 0.5 millimetres, though precision moulded buttons hold tighter limits.

Understanding the ligne is essential when working with legacy patterns, restoring garments, or sourcing replacement buttons from heritage mills. Mixing buttons of similar visual size but measured in different systems can create visible mismatches in a production run; a 20 ligne button and a 50 mm button are close but not identical.