Button Size Chart: Ligne to MM Conversion (Plus What Size to Use)

If you've ever seen a button listed as “24L” and wondered what that means in millimeters, you're not alone. Buttons are measured in a unit called the ligne — here's the full conversion, plus the right size for every garment.

Quick answer
  • A ligne (“L”) is the unit for button diameter. 1 ligne = 0.635 mm (1/40 inch).
  • To convert, multiply ligne by 0.635 for millimeters. Example: 24L × 0.635 ≈ 15 mm.
  • Common sizes: shirts 16–18L, jacket cuffs 24L, jacket fronts 30–34L, coats 40–45L.

What is a ligne?

The ligne is a French unit that has been the global standard in the button trade for over a century. One ligne equals exactly 0.635 mm, or one-fortieth of an inch. It measures the diameter of the button across its face — not the thickness, and not the shank.

Because the ligne is universal across manufacturers, a “32L” button from one mill matches a “32L” from another — which is exactly why the industry never switched to millimeters.

Button size chart: ligne to mm

Ligne Millimeters Inches Commonly used on
14L 9 mm 0.35″ Button-down collar points, sleeve plackets, fine blouses
16L 10 mm 0.40″ Dress shirts, shirt cuffs
18L 11.5 mm 0.45″ Dress shirts, shirt cuffs, blouses
20L 12.5 mm 0.50″ Casual and sport shirts, blouses, light knitwear
22L 14 mm 0.55″ Sport shirts, knitwear, trouser flies
24L 15 mm 0.59″ Jacket cuffs, trousers, waistcoats, cardigans
28L 18 mm 0.71″ Trouser waistbands, cardigans
30L 19 mm 0.75″ Single-breasted jacket fronts, knitwear
32L 20 mm 0.79″ Suit, sport coat and blazer fronts
34L 21.5 mm 0.85″ Larger jacket and blazer fronts
36L 23 mm 0.91″ Double-breasted jacket and blazer fronts
40L 25 mm 1.00″ Single-breasted overcoats, peacoats, chunky cardigans
44L 28 mm 1.10″ Double-breasted overcoats
45L 28.5 mm 1.12″ Double-breasted overcoats
48L 30 mm 1.18″ Oversized overcoats, statement coats
54L 34 mm 1.34″ Statement coats, chunky cardigans, decorative pieces
60L 38 mm 1.50″ Statement coats, decorative pieces
70L 44.5 mm 1.75″ Statement and decorative pieces
80L 51 mm 2.00″ Statement and decorative pieces

Values are rounded. For an exact figure, multiply ligne by 0.635 (mm) or divide millimeters by 0.635 to get ligne. You can also look up any size in our button size chart and converter.

Measuring

How to measure a button

1
Lay it flat
Place the button face-up on a flat surface, or hold it in the jaws of a caliper.
2
Measure the diameter
Measure across the widest point of the cap (the visible face), in millimeters. For oval or novelty shapes, measure the longest dimension; for a shank button, measure the cap only.
3
Convert to ligne
Divide your millimeter measurement by 0.635 — or just find it in the chart above.

What size should you use?

Garment Typical size In mm
Dress shirt (front) 16–18L 10–11.5 mm
Dress shirt (cuffs) 16–18L 10–11.5 mm
Sleeve placket, button-down collar 14L 9 mm
Blouse 14–20L 9–12.5 mm
Suit jacket (front) 30–34L 19–21.5 mm
Sport coat/blazer (front) 30–34L 19–21.5 mm
Double-breasted jacket (front) 32–36L 20–23 mm
Suit/blazer (sleeve/cuff) 24L 15 mm
Trousers/pants 22–28L 14–18 mm
Cardigan/knitwear 20–32L (chunky knits up to 54L) 12.5–20 mm (chunky up to 34 mm)
Overcoat/topcoat 40–45L (48L oversized) 25–28.5 mm (30 mm oversized)
Jeans (tack button) 22–32L (27L standard) 14–20 mm (17 mm standard)
Duffle/toggle coat Toggles, sized by length about 40–55 mm long
Rule of thumb: the cuff button is the same size as the front or smaller. On a dress shirt the cuff matches the front or goes one size down, staying within 16–18L, and the smaller 14L goes on the sleeve placket and button-down collar points. On a suit the sleeve button is six to ten lignes smaller (about twelve on a 36L double-breasted): a suit with 32L front buttons typically pairs with 24L sleeve buttons.

A note on materials and size

Heavier materials can carry a slightly larger size gracefully, while delicate ones look best a touch smaller. A 32L horn button anchors a blazer front; a 16L shell or mother-of-pearl button keeps a dress shirt refined; corozo sizes much like classic shirting; and jean tack buttons are sized across the finished cap, usually 17 mm (27L) on a waistband. New to attaching them? See our guide on how to sew on a button.

Know your size? Shop the buttons.

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Frequently asked questions

What does “L” mean in button sizes?
“L” stands for ligne, the traditional unit for button diameter. 1 ligne equals 0.635 mm, so a 24L button is about 15 mm across.
How many mm is a 24L button?
A 24L button is approximately 15 mm in diameter. To convert any ligne size to millimeters, multiply by 0.635.
What size buttons go on a dress shirt?
Dress shirt front buttons are usually 16–18L (10–11.5 mm). Cuffs take the same size or one size smaller, and the small sleeve-placket button and button-down collar points take 14L.
Is ligne the same as millimeters?
No. Ligne is a fixed unit equal to 0.635 mm. Suppliers list buttons in ligne by convention, then convert to mm.
What is the most common button size?
For shirting, 16–18L (10–11.5 mm) is standard, and 18L is the most common on men's dress shirts. For single-breasted suit and jacket fronts, 30–32L (19–20 mm) is standard; double-breasted fronts go up to 36L (23 mm).