Button Sizes Explained: Ligne to mm Conversion Chart
Button sizing trips everyone up at least once, because the industry uses three systems at the same time: ligne (the trade standard, written “L”), millimetres, and inches. This guide converts between all three and shows you which size belongs on which garment.
Ligne to mm conversion chart
| Ligne | Millimetres | Inches | Typical use |
|---|---|---|---|
| 14L | 9 mm | 3/8″ | Shirt collars, baby clothes |
| 16L | 10 mm | 13/32″ | Shirt plackets |
| 18L | 11.5 mm | 7/16″ | Dress shirts, blouses |
| 20L | 12.5 mm | 1/2″ | Blouses, light dresses |
| 24L | 15 mm | 19/32″ | Cuffs, cardigans, trousers |
| 28L | 18 mm | 23/32″ | Cardigans, skirts |
| 30L | 19 mm | 3/4″ | Jacket fronts (light) |
| 32L | 20 mm | 51/64″ | Jacket & blazer fronts |
| 36L | 23 mm | 7/8″ | Coats, heavy jackets |
| 40L | 25 mm | 1″ | Overcoats |
| 44L | 28 mm | 1 3/32″ | Heavy overcoats |
| 48L | 30 mm | 1 3/16″ | Statement coats, capes |
Bookmark this chart — every listing at Sterling Buttons shows exact mm (and usually ligne), so once you know your target size you can match any of our 1,200+ sewing buttons precisely.
How to measure a button you already have
Lay the button face up on a ruler and measure straight across the widest point in millimetres. Don’t follow the dome’s curve. For shank buttons, ignore the shank — only the face counts. If you’re replacing a lost button, measure one of the surviving ones from the same garment.
Matching buttonholes
A buttonhole is cut to the button’s diameter plus 2–3 mm for thickness. So if your finished buttonholes measure 18 mm, shop for a 15–16 mm (24L) button. Going more than a couple of millimetres under leaves buttons slipping open; over, and they won’t pass through.
Which size for which garment?
Shirts run 10–11.5 mm on the placket, dresses 10–15 mm, cardigans 15–20 mm, jackets and blazers 19–25 mm on the front with 15 mm cuffs, and coats 23–30 mm. When in doubt, larger reads more deliberate than smaller.
Can’t find the button you need? Our Button Finding Service searches thousands of unlisted archive styles — send a photo and rough size and we usually reply within one business day.
Frequently asked
What does ligne mean on buttons?
Ligne (written L) is the traditional button trade measurement. One ligne is about 0.635 mm, so a 40L button is 25 mm across. It dates from 18th-century France and is still how tailors and manufacturers specify buttons.
How do I measure a button in mm?
Lay the button face up and measure straight across the widest point with a ruler in millimetres. Don't measure around the curve — flat across only.
What size button for a buttonhole?
Your buttonhole should be the button's diameter plus 2–3 mm to allow for thickness. Working backwards: a finished 22 mm buttonhole wants a 19–20 mm (30–32L) button.
Are Sterling Buttons listings in mm or ligne?
Both — every listing in the archive shows the exact millimetre size, and most show ligne too, so you can match either a pattern spec or an existing button.
