Manufacturer · Fashion & Home Accessories
YKK zip sizes are indicated by a number – most often No. 3, No. 5, No. 8 and No. 10 – which roughly corresponds to the width of the closed chain in millimetres. The higher the number, the larger the teeth and the greater the load the zip can take. The choice depends on the product, the fabric and the type of zip.
Size is a separate parameter from length. “YKK No. 5, 60 cm” means a chain about 5–6 mm wide and a zip 60 cm long. Here is how to find your way around.
YKK zip sizes – chart
| Number | Width of the closed chain (approximate) | Load | Typical products |
|---|---|---|---|
| No. 2–3 | about 3–5 mm | light | dresses, skirts, blouses, small pockets, purses |
| No. 4–5 | about 5–6 mm | medium | trousers, jeans, sweatshirts, light and mid-weight jackets |
| No. 7–8 | about 7–8 mm | high | winter jackets, workwear, backpacks |
| No. 10 | about 9–10 mm | very high | heavy jackets, holdalls, luggage, technical products |
The values are approximate, because the exact width depends on the product line. A metal, moulded and nylon coil zip with the same number look different, and some intermediate sizes (for example No. 4.5) are only available in certain lines.
How to measure the zip size
- Close the zip completely.
- Using calipers, measure the width of the teeth across the zip – without the tape.
- Round to the nearest whole number in millimetres; this is the approximate number.
- Check the back of the slider – on YKK there is often a number there that confirms the size.
- Identify the line: metal, nylon coil, moulded plastic or invisible zip.
Do not measure the width of the whole tape – it is considerably wider and does not determine the number.
How the size affects the product
Strength
Larger teeth have a bigger interlocking area and withstand stronger crosswise pull. That is why No. 8 or No. 10 is chosen for heavy jackets and luggage, not No. 5.
Weight and flexibility
A bigger zip is heavier and stiffer. On lightweight fabrics a chunky zip “pulls” the placket, creates ripples and looks clumsy. For thin blouses and dresses the small numbers are the right choice.
Look
A chunky zip is a visible feature – often wanted on sportswear and outdoor clothing. A small zip is discreet and suitable for classic styles.
Sewing
The size determines the machine foot, the distance of the seam from the teeth and the width of the fusible tapes. When the number changes, the garment technician must also adjust the pattern of the placket.
Which YKK zip size for which product
- Jeans – metal No. 4–5 with auto-lock.
- Women’s trousers and skirts – invisible zip No. 3 or metal No. 3–4.
- Dress – invisible zip No. 3.
- Sweatshirt – nylon coil or moulded No. 5 with open end.
- Winter jacket – moulded or metal No. 5–8, often two-way.
- Ski jacket – moulded No. 5–8 or nylon coil with a water-repellent coating.
- Backpack – moulded or nylon coil No. 8–10 for the main compartment, smaller for the pockets.
- Leather jacket – metal No. 5–8; at the premium end, a polished metal zip.
Common mistakes when choosing the size
- A zip that is too small on a heavy jacket – the slider loosens and the chain splits.
- A zip that is too large on a lightweight fabric – the product loses its shape.
- Ordering by number only, without stating the line.
- Different zip sizes in the sample and in production – the change is noticed even by the buyer.
Size across the different lines
The same number looks different depending on the line. On a metal zip the teeth are denser and heavier, so a No. 5 metal zip feels more substantial than a No. 5 nylon coil zip. A moulded zip with the same number is lighter than metal but looks chunkier, because the plastic teeth are bulky. Invisible zips are used almost exclusively in small sizes, as they must remain hidden in the seam. With nylon coil zips the number also affects flexibility – small coils follow curves easily, while large ones are stiffer and suit the straight seams of bags and luggage.
Size and tape width
As the number increases, so does the tape width, and with it the width of the placket into which the zip is sewn. If you replace a No. 5 with a No. 8 on an existing style without adjusting the pattern, the zip may not lie correctly or the seam may run too close to the teeth. That is why every change of size is checked with a new sample.
Size and length in one specification
When ordering YKK zips, always state together: line, number, length, type (open end, closed end, two-way), colour according to the YKK colour card, teeth finish and slider type. The length is measured from the top stop to the bottom stop, without the tape above and below them. If the collection has a size range, each garment size usually requires a different zip length. You will find all lines and sizes in the YKK zips category, and for sportswear in YKK moulded plastic zips. If the project does not require YKK, you will also find a suitable size among the metal zips in our general range.
Help with choosing from Polkom
Polkom is a Bulgarian manufacturer of accessories for fashion, furniture, footwear and bags. YKK is a third-party brand whose original zips we supply to brands and manufacturers in Bulgaria and the EU. Send an inquiry describing the product, the fabric and the look you want – we will recommend a size and line and, if needed, arrange samples.
