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Snap Spacing Calculator — Even Snap Placement
Calculate even snap placement and quantities.
How We Calculate This
The first snap sits at the top offset and the last snap sits at the bottom offset, so the remaining snaps divide the span between them into equal gaps. Spacing is the usable span divided by the number of gaps, where the number of gaps is one less than the number of snaps.
The formula
Usable length = Closure − Top offset − Bottom offset − (2 × Placement inset)
Spacing = Usable length ÷ (Snaps − 1)
Placement inset is an optional Advanced Option (default 0). With the default inset the usable length is simply Closure − Top offset − Bottom offset.
Frequently Asked Questions
For babywear: 3-5cm apart. For adult garments: 5-8cm. For home furnishings: 8-15cm. Closer spacing gives a more secure closure but uses more snaps.
Small (8-10mm) for lightweight fabrics and babywear. Medium (12-15mm) for shirts and dresses. Large (17-21mm) for jackets and outdoor wear. The snap should be strong enough to hold but easy to open.
Sew-on snaps are traditional and suit most fabrics. No-sew (prong) snaps punch through fabric with a tool. Magnetic snaps suit bags and purses. Kam snaps are popular for babywear and nappy covers.
Place the ball half on the overlap (right side) and the socket half on the underlap (wrong side). Sew through each hole 4-5 times with a hand needle. Keep stitches small on the right side of fabric.
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Last updated: February 2026
All calculations are estimates. Always verify quantities before cutting or purchasing fabric.