Button Sizes Explained: How to Choose the Right Size for Any Garment
"What size button do I need?" is one of the most common questions in sewing — and one of the easiest to get wrong. Buy a button that's a few millimetres off and it won't sit right, won't pass through the buttonhole, or throws off the whole look of a garment. This guide explains how button sizes work, what size you need for each garment, and how to measure a button you already have.
How button sizes are measured: ligne, mm and inches
Buttons are traditionally measured in ligne (written "L") — an old unit from the textile trade. Most sewing patterns and suppliers still use it, which is why you'll see buttons listed as 18L, 24L or 32L. But customers and patterns often talk in millimetres or inches too, which is where the confusion starts.
The conversion is fixed and simple:
- 1 ligne = 0.635 mm (defined as 1/40 inch)
- To get millimetres: ligne × 0.635
- To get inches: ligne ÷ 40
So a 20L button is 20 × 0.635 = 12.7 mm, or exactly half an inch. If you'd rather not do the maths, our free button size converter does it instantly — type into any field (ligne, mm or inches) and the others update automatically.
Common button sizes at a glance
Here are the sizes used most often in sewing, with what they're typically used for:
- 14L (9 mm) — shirt collars, cuffs and small blouse buttons
- 16L (10 mm) — shirt sleeves and lightweight blouses
- 18L (11.5 mm) — the standard front button for dress shirts
- 24L (15 mm) — jacket sleeves, cardigans and light knitwear
- 32L (20 mm) — suit and blazer front buttons
- 40L (25 mm) — coat and overcoat front buttons
- 44L (28 mm) — heavy overcoats and statement buttons
What size buttons for each garment
If you're matching a specific garment, here's a practical starting point:
Shirts and blouses
Front buttons are usually 18L (11.5 mm), with smaller 14L–16L (9–10 mm) buttons on collars and cuffs. See our shirt buttons.
Suits and blazers
Front buttons are typically 32L (20 mm), with 24L (15 mm) on the sleeves. A single-breasted jacket needs 2–3 front buttons; a double-breasted jacket needs 6. See our suit & blazer buttons.
Coats and overcoats
Coats use larger 40–44L (25–28 mm) front buttons, with 32L (20 mm) on the sleeves. See our coat buttons.
Cardigans and knitwear
Fine-knit cardigans take 24–28L (15–18 mm); chunky knits look best with 32–40L (20–25 mm), which pass more easily through a hand-knitted buttonhole. See our cardigan & sweater buttons.
How to measure a button you already have
Replacing a lost button? The surest way to get the right size is to measure one of the remaining buttons:
- Measure straight across the middle of the button, from edge to edge, in millimetres.
- That measurement is the diameter — match it to the sizes above, or convert it to ligne with our tool.
- Don't have a ruler handy? Our size converter has a clever screen-calibration feature: hold a bank card against your screen to set the scale, then measure your button directly on the display.
Also note the number of holes (most buttons are 2-hole or 4-hole) and the material and finish, so your replacement matches the rest of the garment.
Still not sure? See it before you buy
If you want to see how a size and colour will actually look on your garment, try our free button try-on tool — upload a photo of your shirt, jacket or coat and preview any button from our range, at the right scale, directly on it.
Once you know your size, browse the full range at buttonary.com — with no minimum order, you can buy a single replacement button or a full set.
Once you've chosen your button, learn how to sew it on, step by step with photos for every stage.