Buttonhole Spacing Calculator
Calculates the exact center-to-center spacing between buttonholes on a garment placket for perfectly even results. Use it whenever you are adding buttons to shirts, cardigans, or any faced opening.
About this calculator
Even buttonhole spacing is achieved by dividing the usable placket length — after reserving a margin at the top and bottom — equally among the gaps between buttons. With n buttons there are n − 1 gaps, so the spacing formula is: spacing = (placketLength − topMargin − bottomMargin) / (numberOfButtons − 1). The topMargin and bottomMargin reserve fabric at each end so the first and last buttonholes are not too close to the edge. A typical margin is 1/2" to 1" depending on the garment type and button size. The result is the distance from the center of one buttonhole to the center of the next. Once you have the spacing, mark the first buttonhole position at topMargin from the top edge, then mark each subsequent buttonhole at intervals of the calculated spacing down the placket.
How to use
You are making a shirt with a 14" placket and 6 buttons. You want a 3/4" top margin and a 3/4" bottom margin. Step 1 — subtract margins from placket: 14 − 0.75 − 0.75 = 12.5" usable length. Step 2 — divide by (buttons − 1): 12.5 / (6 − 1) = 12.5 / 5 = 2.5" spacing. Step 3 — mark positions: first buttonhole at 0.75" from top, then at 3.25", 5.75", 8.25", 10.75", and 13.25" (= 0.75" from bottom). All six buttonholes are evenly spaced at 2.5" apart.
Frequently asked questions
How do I determine the correct top and bottom margin for buttonhole placement?
A good rule of thumb is to set the top and bottom margins equal to the radius of the button — roughly half the button diameter — but no less than 1/2". This ensures the first and last buttons sit visually balanced within the placket without crowding the edge. For neckline closures, the top buttonhole is often placed at the neckline seam itself, which sets your top margin to zero or very small. Always check against your pattern's markings if you are adapting an existing design.
What is the standard buttonhole spacing for a dress shirt versus a cardigan?
A classic men's dress shirt typically spaces seven buttons over a front placket of roughly 27", yielding about 3.5" to 4" between buttonholes. Cardigans and casual knitwear often use 5–7 buttons with slightly wider spacing — 3" to 5" — depending on the garment length and style. Children's garments use closer spacing (1.5"–2") for a neat look and easier fastening. The calculator lets you customise all these variables to suit any specific garment.
Why does the buttonhole spacing formula divide by numberOfButtons minus 1?
The number of spaces between n evenly distributed points is always n − 1, not n. Think of a fence: 4 fence posts create 3 gaps between them. Similarly, 6 buttons create 5 intervals across the placket. Dividing by n instead of n − 1 is a common error that results in the last button being placed one interval short of the bottom margin. Using n − 1 guarantees the spacing is symmetrical and that both end margins are respected exactly as entered.