Film thickness is the most overlooked parameter when sourcing poly bags for garment packaging, yet it directly affects cost, protection and the customer's unboxing experience. Too thin, and garments risk moisture or scratches; too thick, and both cost and environmental pressure rise. This guide helps you understand gauge conversion and how to choose the right thickness, so every packaging dollar is well spent.

1. Si, Micron & Millimeter: Gauge Conversion

In China, film thickness is commonly expressed in 'si': 1 si equals 0.01mm, or 10 microns. European and American customers usually use microns or mils (1 mil ≈ 25.4 microns). Always confirm the unit before ordering to avoid a '10x thickness' misunderstanding.

ThicknessmmMicronsCommon Uses
0.5 si0.005mm5μmSmall parts bags: hang tags, buttons
1 si0.01mm10μmStandard inner bags, single T-shirt bags
1.5 si0.015mm15μmRegular flat garment bags
2 si0.02mm20μmHeavier garments: jackets, jeans
3 si0.03mm30μmPremium garments, multi-piece sets
4 si & above0.04mm+40μm+Heavy items, hardware trims, industrial use

2. Which Thickness for Which Use

A general rule: inner bags can be thin, outer packaging bags should be thicker. For garments displayed on hangers and orders shipped by sea, 2 si or above is recommended; for e-commerce dispatch bags, balance protection against cost.

  • OPP bags are stiffer than PE at the same thickness — better for display packaging
  • Packaging that is opened repeatedly (e.g. in-store) calls for resealable or thicker bags
  • Garments with metal zippers or buttons should be wrapped in tissue paper first to avoid puncturing the bag

3. Thickness vs Clarity, Stiffness & Load

With the same material, a thicker bag means lower clarity, higher stiffness and higher load capacity; but thickness cannot be compared directly across materials. For instance, 1.5 si OPP is stiffer than 2 si PE, with better clarity and print results. Always consider material and thickness together.

4. How to Measure & Inspect Film Thickness

The most reliable method is a film thickness gauge: measure several points on the bag mouth and body and take the average. Factories also do batch sampling before shipment. 'Feeling' the thickness by hand is unreliable, since different materials feel very different. If thickness falls short, ask the factory to re-ship or handle it per contract.

5. Selection by Category & Sampling Tips

Before placing a bulk order, ask your supplier for samples of different thicknesses and test them with real garments: bagging, sealing, stacking and rough transport, then check for tears or fogging. Dongguan TAGE Packaging offers poly bags in various materials and thicknesses plus eco paper bag options, and can recommend the most economical solution for your garment category.

💡 Tip: cross-border sellers often get bad reviews for bags that are 'too thin and tear easily'. For e-commerce orders to Europe and the US, use at least 1.5 si for single items and 2 si or more for garments with zippers or metal hardware.

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