Quick answer: Button size is measured in ligne (abbreviated L), the international standard for apparel. 1 ligne = 0.635 mm. To find a button’s ligne, measure its diameter in millimeters and divide by 0.635. Example: a 20 mm button = 32L.
If you’ve ever seen a button listed as “24L” or “32L” and had no idea what it meant, you’re not alone. This guide explains the ligne system, gives you a full conversion chart, and shows exactly how to measure a button so you order the right size every time.
What is a ligne (L)?
Ligne (pronounced “line”) is the traditional unit used to measure button diameter across the garment industry worldwide. It is written as L or with the prime symbol ”’.
- 1 ligne = 0.635 millimeters = 1/40 inch
- 40 ligne = 1 inch = 25.4 mm
The ligne measures the diameter of a round button. For non-round buttons, it refers to the largest width.
How to convert between ligne, mm, and inches
Use these two simple formulas:
- Millimeters → Ligne:
mm ÷ 0.635 = L - Ligne → Millimeters:
L × 0.635 = mm
Worked example: You have an 18 mm button. 18 ÷ 0.635 ≈ 28L.
Button size conversion chart (ligne → mm → inches)
| Ligne (L) | Millimeters | Inches | Common use |
|---|---|---|---|
| 14L | 9 mm | 0.35″ | Baby clothes, doll clothing |
| 16L | 10 mm | 0.39″ | Shirt cuffs and sleeves |
| 18L | 11.5 mm | 0.45″ | Dress shirt fronts |
| 20L | 12.5 mm | 0.50″ | Blouses, light shirts |
| 24L | 15 mm | 0.59″ | Cardigans, blouses |
| 28L | 18 mm | 0.71″ | Light jackets, dresses |
| 32L | 20 mm | 0.79″ | Blazers, suit jackets |
| 36L | 23 mm | 0.91″ | Suit jackets, light coats |
| 40L | 25.4 mm | 1.00″ | Coats, outerwear |
| 45L | 28.5 mm | 1.12″ | Heavy overcoats |
| 54L | 34 mm | 1.34″ | Decorative & statement buttons |
Recommended button sizes by garment
| Garment | Typical button size |
|---|---|
| Dress shirt (front) | 16L–18L |
| Blouse | 18L–24L |
| Cardigan / knitwear | 24L–32L |
| Blazer (front) | 32L–36L |
| Blazer (sleeve) | 24L |
| Suit jacket (front) | 34L–36L |
| Overcoat | 36L–45L |
How to measure a button (step by step)
- Lay the button flat on a millimeter ruler or use calipers for precision.
- Measure the diameter across the widest point, edge to edge.
- Convert to ligne by dividing the millimeter value by 0.635.
- Round to the nearest standard size (buttons come in fixed ligne increments).
Tip: If you don’t have a ruler, place the button against a coin of known diameter to estimate, then refine with the chart above.
Why getting the size right matters
- Buttonhole fit: A button that’s too big won’t pass through; too small and it slips open. The buttonhole is usually cut slightly longer than the button diameter.
- Proportion and style: Oversized buttons on a fine shirt look clumsy; tiny buttons on a heavy coat look weak.
- Bulk orders: For manufacturers, ordering the wrong ligne across thousands of units is a costly mistake — always confirm with a physical sample first.
Frequently asked questions
What does 24L mean in button sizing?
24L means 24 ligne, which equals about 15 mm (0.59 inches) in diameter. It’s a common size for cardigans and blouses.
How many millimeters is a 32L button?
A 32L button is 20 mm in diameter (32 × 0.635 = 20.3 mm).
How do I convert button size from mm to ligne?
Divide the diameter in millimeters by 0.635. For example, 15 mm ÷ 0.635 ≈ 24L.
What size button is best for a dress shirt?
Most dress shirts use 16L–18L buttons on the front (about 10–11.5 mm), with smaller buttons on the cuffs.
Is ligne the same everywhere?
Yes. Ligne is the international apparel standard, so 32L means the same diameter (about 20 mm) regardless of country or brand.