Button Spacing Calculator

The math is simple. The placement decisions are not.

Even button spacing is straightforward arithmetic: distance between buttons equals usable length divided by gaps, where gaps = (button count minus one). For a 55 cm placket with a 2.5 cm margin top and bottom and 6 buttons, you get 50 cm of usable length divided into 5 gaps, or exactly 10 cm between buttons.

But evenly spaced buttons are not always the right answer. Garment construction has rules about where each button must land regardless of math.

Anchor points that decide button placement

A shirt or blouse needs a button at three specific locations before you space anything evenly:

• Bust apex. The fullest point of the chest. A button here prevents the placket gaping open (the “bust gap”). On a women’s shirt, fitting a button at the apex is non-negotiable.
• Waist. At the natural waist if the garment is fitted, prevents pull at the front waist.
• Top button. About 1 cm below the collar attachment, hidden under the collar stand when buttoned.

Space the remaining buttons evenly between those fixed points, not against the total garment length. A common beginner mistake is to math out perfectly even spacing on a finished pattern, only to end up with no button at the bust apex and a permanent gap there.

Number of buttons by garment

Buttonhole orientation rule

Horizontal buttonholes on plackets and waistbands, vertical buttonholes on narrow shirt fronts. Horizontal holes let the button shift sideways under tension without unbuttoning, which is why coats and waistband closures use them. Vertical holes lie flatter and look cleaner on a thin placket where the button has nowhere to drift.

The buttonhole length is the button diameter plus its thickness, never just the diameter. A 1.5 cm button with a flat 2 mm shank needs a 1.7 cm buttonhole. Cut on the short side, then test, then extend if needed.

Marking the placement on the actual fabric

Mark from the finished neckline down, not from the cut edge. Cut edges get hemmed, gathered, or trimmed, so they are not a stable reference. Use tailor’s chalk or a removable fabric marker, and pin-mark before cutting any buttonhole. Once cut, you cannot move the hole if you measured wrong.

Children’s garments — keep spacing tighter (4 to 6 cm). And for anything sized under three years old, skip buttons entirely and use snaps. Buttons are a choking hazard.