Button & Buttonhole Spacing Calculator

The math behind even spacing

The first and last buttons sit at your chosen offset from each end. Everything between them needs to divide the remaining distance into equal gaps: spacing = (placket length − 2 × offset) ÷ (number of buttons − 1).

Where to place the first button

The offset for the top button on a shirt is usually driven by the collar or neckline construction rather than pure math — leave enough room that the top buttonhole doesn't sit right at a seam or fold. The bottom offset just needs to clear the hem allowance.

Stress points still need their own button

Pure even spacing can land a button in an awkward spot — at the fullest point of a bust, for instance, or right at a waistline. It's common practice to place buttons at those stress points first, then space the rest as evenly as possible around them rather than forcing perfectly equal math everywhere.