Grip seal and zipper bags are sized as width × length of the flat bag in millimetres, with the opening on the width side. To find your size, add the thickness of the product to both its width and its length, then add 15–25 mm above the product for the closure. Thickness is quoted per wall in microns: around 40–50 µm suits light items, 75–100 µm heavier or sharper ones.
Resealable bags are sized as width × length of the flat, empty bag, in millimetres:
So a 160 × 250 mm bag is 160 mm wide at the opening and 250 mm deep. Two things catch buyers out. Some catalogues list the size the other way round, so always check which number is the opening. And the closure profile sits 10–20 mm below the top edge, so part of the length is not usable for the product.
The same sizing applies to grip seal (press-to-close) bags and slider zipper bags. The slider adds a few millimetres at the top, but the bag is measured the same way.
A flat bag loses width and length as soon as it has to wrap around something with thickness. Use this rule:
Example: a folded scarf of 150 × 200 × 20 mm needs a bag of about 180 × 240 mm. A 160 × 250 mm bag would be too narrow; 200 × 300 mm fits with room to spare.
The table shows sizes you will often see in European catalogues, with typical contents. These are common sizes, not limits: resealable bags can be made to any width and length.
| Size (W × L, mm) | Typical contents |
|---|---|
| 40 × 60 | Buttons, beads, spare screws, single earrings |
| 60 × 80 | Rings, small jewellery, tablets in blister strips |
| 80 × 120 | Seeds, small components, trading cards |
| 100 × 150 | Samples, phone accessories, cosmetics minis |
| 120 × 170 | Socks, small cosmetics, A6 leaflets |
| 160 × 250 | Underwear, small textiles, A5 documents |
| 230 × 320 | A4 documents, T-shirts folded flat |
| 250 × 350 | Folded garments, catalogues |
| 300 × 400 | Knitwear, multi-item packs |
| 400 × 500 | Bedding, bulky textiles |
In Europe, bag thickness is quoted per wall in microns (µm). A 50 µm bag has two walls of 50 µm each. UK suppliers may use gauge instead (1 µm = 4 gauge), and US suppliers use mil (1 mil = 25.4 µm). Our micron, gauge and mil converter does the maths.
| Contents | Typical starting point |
|---|---|
| Light items: samples, cards, leaflets | 40–50 µm |
| Textiles, cosmetics, small parts | 50–75 µm |
| Heavy items, hardware, sharp edges | 75–100 µm or more |
Starting points from common practice. Test with your heaviest and sharpest product. Our guide to mailing bag thickness in microns explains the trade-off between film weight and strength.
For small, flat items, sending a grip seal bag as a large letter is often cheaper than a parcel. Each country sets its own limits. At the time of writing, the national operators publish these maximums:
| Country, format | Max size | Max weight |
|---|---|---|
| Germany, Großbrief | 353 × 250 × 20 mm | 500 g |
| Germany, Maxibrief | 353 × 250 × 50 mm | 1,000 g |
| France, Lettre verte (domestic) | L + W + T under 100 cm, length max 60 cm, thickness max 3 cm | 2 kg |
| Italy, Posta Ordinaria "Medio Standard" | 353 × 250 × 25 mm | 2 kg |
| Spain, Carta ordinaria (non-standard) | L + W + T up to 90 cm, no side over 60 cm | 2 kg |
Germany will change its formats on 1 January 2027. According to Stiftung Warentest, the Großbrief will then allow up to 30 mm and 1,000 g, and the Maxibrief up to 381 × 305 × 30 mm and 2,000 g. If you post thicker items as a Maxibrief today, plan for the new 30 mm limit.
Thickness is the limit you hit first. A bag that is too big lets the product move and adds height at the folds. A snug bag keeps the packet flat.
| Grip seal (press-to-close) | Slider zipper | |
|---|---|---|
| Opening and closing | Press the profiles together by hand | Pull the slider |
| Best for | Small parts, samples, single use or a few re-uses | Clothing, food at home, frequent re-use |
| Profile | Flat and light | Slightly bulkier at the top |
| Ease of use | Needs some finger strength | Easy for all users |
Both can have a white write-on panel, a hang hole, or a printed design.
If the bag will hold food, it has to be suitable for food contact. In the EU, plastic food contact materials are covered by Regulation (EU) No 10/2011. Ask the supplier for a written declaration of compliance for your intended use (type of food, temperature, contact time) before you pack food.
We produce grip seal and slider zipper bags to order in our own factory in Istanbul. Width, length, thickness and print are set to your product, so the sizes in this guide are a starting point, not a limit. Send us your product dimensions and we will suggest sizes and send free samples to test.
As width × length of the flat bag, in millimetres. Width is the side with the opening, length runs from the opening to the bottom. Part of the length sits above the closure, so the usable length is shorter.
A grip seal bag closes by pressing two interlocking profiles together. A slider zipper bag has a plastic slider that opens and closes the profile. Sliders are easier to use repeatedly; press seals are flatter and usually lighter.
It depends on the contents. Thickness is quoted per wall in microns. Light items such as samples or small parts work in thinner film; heavy, sharp or pointed items need thicker film. Test with your own product.
Often, if the packed bag stays within the national postal limits for large letters. In Germany a Großbrief may be up to 353 × 250 × 20 mm and 500 g; in France a letter may be up to 3 cm thick. Check the current rules of your postal operator.
Only if the bag is made for food contact. In the EU, plastic food contact materials fall under Regulation (EU) No 10/2011, and the supplier should give you a written declaration of compliance for the intended use.
This guide is general information based on published sources at the time of writing. It is not legal or tax advice.
Tell us what goes in the bag and we will send free grip seal and zipper bag samples in the sizes and thicknesses that fit.