Buttonhole Spacing Calculator
Calculate the center-to-center distance between buttonholes on a placket for evenly spaced results. Use it whenever adding buttons to a shirt, cardigan, blouse, jacket, or any faced opening.
Last updated: May 2026
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About this calculator
The formula is: spacing = (placketLength − topMargin − bottomMargin) / (numberOfButtons − 1). The placket length is the total length of the opening (typically from neckline to hem); topMargin and bottomMargin are the distances from the edges of the placket to the first and last buttonhole. Subtracting these gives the usable distance to distribute buttonholes evenly. Dividing by (numberOfButtons − 1) — not numberOfButtons — produces the gap between adjacent buttonholes, because n buttons create n−1 gaps between them. Edge cases: only one button (numberOfButtons = 1) produces division by zero — a single button does not have spacing; place it wherever the design calls for. Standard spacings by garment type: button-front dress shirts typically have 4–6 inches between buttons (more for men's, less for women's, depending on size); cardigans and jackets typically 3–4 inches; baby and children's clothing 2–3 inches; long coats 4–6 inches between center buttons. The first and last buttonholes have functional placement requirements: the top button (collar button on dress shirts) sits 1/2 to 3/4 inch below the neckline edge to control collar shape; the bottom button on shirts and jackets sits 1 to 2 inches above the hem (or just above the waist for tucked-in shirts); the first button below the bust on shirts sits at the bust apex to prevent gaping. For women's shirts, the most common gaping problem is between the bust and waist — place an extra button at the bust apex if gaping is a fitting issue. Always sew a test buttonhole on scrap of the same fabric and interfacing before sewing the real ones; thread tension, foot pressure, and fabric thickness all affect buttonhole consistency.
How to use
Example 1 — Women's dress shirt. 28-inch placket from neckline to hem; 8 buttons; 1-inch top margin (collar button); 1-inch bottom margin (above hem). Enter placketLength 28, numberOfButtons 8, topMargin 1, bottomMargin 1. Result: (28 − 1 − 1) / (8 − 1) = 26 / 7 ≈ 3.71 inches between buttons. ✓ For better gape prevention at the bust, manually adjust — place buttons at 1 inch (collar), 4.5 inches (chest), 7.5 inches (bust apex — this is a critical anti-gape position), 10.5 inches (waist), 14, 18, 22, 27 inches. Slight asymmetric spacing prevents gaping where it matters most. Example 2 — Cardigan. 22-inch placket length; 5 buttons; 1/2-inch top margin; 1/2-inch bottom margin. Enter 22, 5, 0.5, 0.5. Result: (22 − 0.5 − 0.5) / (5 − 1) = 21 / 4 = 5.25 inches between buttons. ✓ Five buttons at 0.5, 5.75, 11.0, 16.25, 21.5 inches from the top of placket — even spacing perfect for a casual cardigan. For chunky knits and bulky yarns, consider fewer larger buttons (3–4 at wider spacing) for visual balance.
Frequently asked questions
How many buttons should I use on my project?
Depends on garment type, fit, and aesthetic. Men's dress shirts: typically 7–8 buttons (collar button, 6–7 down the front, sometimes 2 cuff buttons). Women's dress shirts: typically 6–8 buttons depending on length; an extra button at the bust apex prevents gaping for fitted styles. Cardigans and casual knits: 4–6 buttons typically; chunky knit cardigans may use just 3 large buttons. Jackets and blazers: single-breasted suit jackets typically 2 (one button) or 3 (two button — only top button buttoned) on the front; double-breasted jackets 6–8 in two parallel rows. Coats: 5–6 buttons for full-length coats; trench coats often 10 (in double rows). Baby and children's clothing: smaller items use fewer buttons (3–4); large smock dresses may use 8–10 small buttons. Decorative button bands (no functional buttons, purely visual): can use many buttons for design effect. For fitting purposes, more buttons mean better fit (less gaping between fastener points); fewer buttons mean a cleaner aesthetic but require careful tailoring to prevent gaping at stress points (bust, hip).
Where should I place the first and last buttons?
The first button (top) on a button-front shirt sits 1/2 to 3/4 inch below the neckline edge to allow the collar to close cleanly. For collarless or low-neckline garments, the top button sits 1/4 to 1/2 inch below the placket edge. The last button (bottom) on shirts sits 1 to 1.5 inches above the hem so the shirt drapes without the bottom button being directly at the hem (looks sloppy). On jackets and coats, the bottom button sits at the natural waist or 1–2 inches below depending on style. Critical position: on women's fitted shirts, place a button at the bust apex (the fullest point of the bust) — this is the most common gaping location and a button there pulls the placket flush. For women's shirts and dresses, also place a button at the natural waist if the design has waist shaping. The "magic" middle buttons are evenly spaced between these functional positions; the calculator handles the even spacing once you fix the functional positions at the top and bottom.
What size button should I use?
Match button size to garment weight and proportions. Standard sizes (in "lignes" — 40 lignes = 1 inch — or in mm/inches): 14 ligne (9mm, 3/8 inch) for baby/children, shirt sleeves, small details; 16 ligne (10mm, 7/16 inch) for women's blouses; 18 ligne (11.5mm, 1/2 inch) for men's shirt fronts; 20 ligne (13mm, 9/16 inch) for shirt collars and women's cardigans; 24 ligne (15mm, 5/8 inch) for blazers and lightweight jackets; 28–32 ligne (18–20mm, 3/4 inch) for jackets, vests, women's coats; 36–40 ligne (22–25mm, 7/8 to 1 inch) for full-length coats; 45 ligne and up (28mm+) for chunky knits, statement buttons, decorative use. Buttonhole length should be the button diameter plus 1/8 inch — too small and the button is hard to fasten; too large and the button slips loose. For shanked buttons (with a loop on the back), use the diameter of the button, not the shank. For thick fabrics (wool coats), buttonholes need to be larger to accommodate the fabric bulk going through.
What are the most common buttonhole mistakes?
The biggest is uneven spacing because the calculator was used incorrectly — dividing by numberOfButtons instead of (numberOfButtons − 1) gives n−1 evenly-spaced buttons in n+1 slots. The second is buttonholes too small for the button; the button cannot pass through or the buttonhole tears with use. Always sew a test buttonhole on scrap fabric and try the button; adjust before sewing real buttonholes. The third is buttonhole direction inconsistent with the placket; horizontal buttonholes are used on most shirt plackets (button pulls horizontally to stress); vertical buttonholes on cuffs and some specialty applications. The fourth is forgetting interfacing under the buttonhole; without stiff interfacing, the buttonhole stretches and distorts after wearing. Use heavy fusible interfacing in the placket area before sewing. The fifth is poor thread tension or wrong needle; buttonholes are sewn slow and steady with a sharp needle and fresh thread to get clean stitches. The sixth is failing to add the bust-apex button on women's fitted shirts; even spacing without this button leaves a gap at the bust. The seventh is sewing buttons opposite buttonholes in the wrong position — the button must be centered on the buttonhole when closed; mark button positions by inserting a pin through the closed buttonhole and marking where it pierces the under-layer. The eighth is using buttons too small for the fabric weight; small buttons on heavy coats look fragile and pull through; match button visual weight to fabric.
When should I not use this calculator?
Skip it for non-buttoned closures: zippers, snaps, hook-and-eye, velcro, ties, frogs, toggle closures all have completely different placement logic. It is the wrong tool for asymmetric buttonhole arrangements where buttons are intentionally non-evenly spaced (double-breasted jackets with two columns of buttons; ornate Victorian-style closures with grouped buttons). Do not use it for fly-front closures (concealed plackets with hidden buttons or zippers) where the visible front and hidden inner placket have different placements. For non-functional decorative buttons (button bands sewn closed for design only), spacing is purely aesthetic and the formula's functional requirements (gape prevention, ease of fastening) do not apply. For shirts with custom fit issues (bust gaping, hip gaping), use a fitting-driven approach: identify the gaping points first, place buttons there, then space the remaining buttons evenly between fixed positions. And for ready-to-wear modifications where you are altering an existing garment's button placement, measure the existing buttons first and decide whether to move all or just add new ones; the formula assumes a fresh design.