Manufacturer · Fashion & Home Accessories
Spiral zipper size 5 is the most versatile: its coil is about 5 mm wide when closed and suits trousers, sweatshirts, light jackets, bags, and cases. Size 3 is chosen for dresses, skirts, and fine textiles, while sizes 8 and 10 are for tents, luggage, tarps, and upholstery where the zipper must withstand heavier loads.
What the spiral zipper size means
The zipper size is an industrial designation for the coil width. For spiral zippers, it approximately corresponds to the width of the two interlocked coils in millimetres – size 5 is about 5 mm, size 8 about 8 mm. The size is not an exact measurement: it may vary slightly between manufacturers, but the reference is consistent.
The size determines three things simultaneously:
- Strength – larger coils withstand greater lateral and longitudinal stress.
- Appearance – smaller sizes are more discreet; larger sizes are visible and sporty.
- Compatibility with slider – sliders are selected for a specific size and coil type.
The tape width also increases with size but is not part of the size designation. If the zipper must fit a specific seam or edge, request a sample and measure the tape.
Table: Spiral zipper sizes 3, 5, 8, and 10
| Size | Approximate Coil Width | Load Capacity | Typical Products |
|---|---|---|---|
| 3 | about 3–4 mm | Light | Dresses, skirts, blouses, children's clothing, pockets, cushions, wallets |
| 4–4.5 | about 4–4.5 mm | Light to medium | Trousers, thicker skirts, small bags |
| 5 | about 5 mm | Medium | Sweatshirts, light jackets, tracksuits, bags, toiletry bags, cases, backpacks |
| 7–8 | about 7–8 mm | High | Tents, sleeping bags, travel bags, tarps, equipment cases |
| 10 | about 10 mm | Very high | Luggage, upholstery, tarpaulins, industrial covers |
Some intermediate sizes are only available from certain manufacturers. If your specification requires an exact size, please specify it in your inquiry.
How to choose a spiral zipper size
1. Load on the zipper
Consider how much stress the zipper will endure when closed. A body-hugging dress, a fully packed backpack, or a tarp stretched by wind all apply transverse load to the coil. When in doubt, choose one size larger – the cost difference is usually minor compared to a product complaint.
2. Fabric thickness and weight
Fine fabric with a large coil zipper looks heavy and may pucker. Thick fabric with a very fine zipper makes the seam stiff and the zipper appear “lost.” The proportion between fabric and coil is both an aesthetic and functional consideration.
3. Opening shape
The coil is flexible at all sizes, but finer coils bend with a smaller radius. For rounded openings on toiletry bags and small pouches, sizes 3 and 5 are easier to sew than size 8.
4. Appearance and brand
For sports and outdoor collections, a large coil is often part of the design. For formal wear, the zipper should be as discreet as possible – then a smaller size or an invisible zipper is chosen.
5. Slider and puller
A larger size allows a bigger slider and a more comfortable puller that can be handled with gloves. This is important for tents, jackets, and luggage.
Example: sizes in one collection
A sportswear brand may comfortably work with just two sizes. Size 5 covers sweatshirts, vests, tracksuits, and jacket pockets, while size 3 is for leggings pockets, zip-neck T-shirts, and children’s models. If backpacks or sports bags are included, size 8 is added for the main opening. This keeps inventory simple, sliders are ordered in three sizes, and colours are easily coordinated across products. The same logic applies to home textiles: size 3 for pillowcases and size 5 for mattresses and heavier covers.
How to measure an existing zipper size
- Close the zipper completely.
- Use calipers or a ruler to measure the width of the two interlocked coils – excluding the tape.
- Round to the nearest standard size (3, 5, 8, or 10).
- Check the size printed on the back of the slider – often the size and coil type letter are indicated there.
If measuring for replacement in a production item, send a physical sample to the manufacturer – this avoids differences in coil profile and slider height.
Common mistakes when choosing a size
- Everything with size 5. The universal size is convenient but looks heavy on dresses and is borderline for tents.
- Different sizes in one collection without reason. This complicates inventory and slider ordering.
- Size without coil type. “Zipper size 5” can be spiral, moulded plastic, or metal – always specify the coil type.
- Ignoring length. A long zipper on a large opening endures greater load and often requires a larger size.
If you hesitate between spiral and other coil types for high load, compare sizes also in the moulded plastic zips category. Our full range of spiral zippers is available in various sizes, lengths, and colours.
Spiral zipper size 5 and other sizes from Polkom
Polkom is a manufacturer of accessories for fashion, furniture, footwear, and bags based in Sofia with over 30 years of experience. We offer spiral zippers in main sizes – in standard lengths and by the metre, with sliders featuring logos and custom colours. If you are unsure which size suits your product, send us a description or fabric sample via the inquiry form – we will suggest options and provide samples.
