Zip Length Calculator

For a dress back zip, measure from the top of the zip opening (usually neckline seam) to the bottom of the zip opening (waist or hip). For a skirt, measure from waistband seam to hip. For a trouser fly, measure from the waistband to the bottom of the fly shield. Always buy the next size up if between standard sizes.

Standard zip lengths in centimetres are: 10, 12, 15, 18, 20, 22, 25, 28, 30, 35, 40, 45, 50, 55, 60 and longer. YKK concealed (invisible) zips are commonly stocked in 20, 23, 25, 30, 35, 40, 45, 50, 55 and 56cm. Always buy the nearest size equal to or longer than your measured opening — ideally 2.5–5cm longer so the slider has room at the bottom.

Invisible zips are ideal for dresses, skirts and anywhere you want the zip hidden. The teeth fold behind the fabric so only the pull tab is visible. They require an invisible zip foot on your sewing machine. They are not suitable for heavy-duty applications.

Closed-end zips have a stop at the bottom and are used for skirts, dresses and bags. Open-ended (separating) zips split completely apart and are used for jackets, coats and cardigans. Two-way zips can open from both ends.

Yes. Nylon and moulded zips can be shortened by stitching across the teeth at the desired length with a zigzag stitch, then cutting off the excess below. Metal zips can also be shortened but you may need to remove individual teeth with pliers. Always shorten from the bottom.