Buttonhole Spacing Calculator

Gaps, not buttons

Even spacing divides the distance between the first and last buttons by the number of gaps, and there is always one fewer gap than there are buttons. Six buttons have five gaps.

Dividing by the button count instead is why a set of buttonholes comes out short of the intended last position — the error is one gap's worth, which on a shirt front is three or four inches.

The first and last positions are design decisions rather than outputs. One of them should sit at the fullest point of the bust, because that is where a front placket pulls open and where even spacing elsewhere does not help.

A worked example

Six buttons from 2 inches below the neckline to 22 inches: a 20 inch span over five gaps, so 4 inch spacing, with buttons at 2, 6, 10, 14, 18 and 22.

Divide by six instead and the spacing is 3.33, putting the last button at 18.67 — over three inches short of where the placket needed it to end.

Where the answer misleads

Perfectly even spacing is not always right. If the bust point falls between two evenly spaced buttons, the placket will gape there regardless, and the correct answer is to place one button at the bust point and space the others around it — accepting slightly uneven gaps for a garment that stays closed.

Button size affects perceived spacing. Large buttons at a spacing that looks generous on small ones can look crowded, so the number of buttons is worth revisiting when the button changes.

Finally, horizontal buttonholes on a placket sit slightly off-centre, the button pulls to the end of the hole nearest the edge, so the buttonhole starts about an eighth of an inch beyond the centre line rather than on it.