How do I calculate even button spacing?

Subtract the top and bottom offsets from the placket length, then divide by the number of gaps (buttons minus 1). This gives the distance between each button centre.

How long should buttonholes be?

Buttonhole length equals the button diameter plus 3mm. For thick or domed buttons, add the button thickness as well. Always test on a scrap of fabric first.

Where should the first and last buttons go?

The top button is usually 1.5-2.5cm from the neckline edge. The bottom button is 2-3cm from the hem. For womens shirts, place a button at bust level to prevent gaping, then space the rest evenly.

Should I mark button or buttonhole positions first?

Mark buttonhole positions on the overlap side first. Sew the buttonholes, then lap the garment closed and mark button positions through the buttonholes to ensure perfect alignment.

SewCalcs

Button Spacing Calculator — Even Placement

Calculate even button spacing and placement for garments.

Placket Length

Top to bottom of button area

Button Diameter

Number of Buttons

Top Offset

Distance to first button

Bottom Offset

Distance from last button to end

How We Calculate This

Even spacing is calculated by dividing the usable placket length by the number of gaps between buttons.

The formula

Usable length = Placket - Top offset - Bottom offset

Spacing = Usable length ÷ (Buttons - 1)

Buttonhole = Button diameter + 3mm

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify quantities before cutting or purchasing fabric.