Mailing Bag Size Guide: How to Choose the Right Poly Mailer

In short: Mailing bag sizes are width x length + adhesive flap in centimetres; add about 2–3 cm to the product's width and thickness to find the bag width.

How to read the size

A mailing bag described as 30 x 38 +5 cm is 30 cm wide and 38 cm long inside, plus a 5 cm self-adhesive flap that folds over the opening. The flap is not usable space. On bags with a handle, a second figure (for example +5+7) adds the 7 cm handle section.

A simple sizing rule

Width: product width + product thickness + 2–3 cm.
Length: product length + product thickness + 3–4 cm, so the flap closes without strain.
For soft goods that can be folded, fold to the bag rather than buying a bigger bag — postal rates often depend on dimensions as well as weight.

Size suggestions

Bag size (cm)	Inches (approx.)	Typical products
22 x 30 +5	8.7 x 11.8 +2	T-shirts, underwear, accessories, A4 documents and catalogues
25 x 30 +5	9.8 x 11.8 +2	Folded shirts, leggings, small textile sets
30 x 38 +5	11.8 x 15 +2	Shirts, blouses, folded trousers, light knitwear
35 x 45 +5	13.8 x 17.7 +2	Sweatshirts, jeans, dresses, bedding sets
45 x 55 +5	17.7 x 21.7 +2	Coats, jackets, bulky textiles, multi-item orders

Which type of mailer?

Mailing bags with a document pocket — a clear self-adhesive pocket on the front holds the invoice, so you do not need a separate packing list envelope.
Plain mailing bags — the lowest cost per shipment when no document travels outside.
Clear mailing bags — for catalogues, magazines or goods that should be visible.
Mailing bags with a handle — double as a carrier bag for boutiques and showrooms.
Bubble mailers — an air-bubble lining protects cosmetics, electronics accessories, books and fragile items.

Opaque film and security

Except for the clear range, our poly mailers use opaque film so contents cannot be seen. The adhesive strip is permanent: once the bag has been opened it cannot be resealed without visible damage, which discourages tampering in transit.

Frequently asked questions

What does +5 cm mean in a mailing bag size?

It is the length of the self-adhesive closing flap. A 30 x 38 +5 cm bag has a 30 x 38 cm usable inside area plus a 5 cm flap that folds over to seal it.

What size mailing bag do I need for a hoodie?

A folded hoodie or sweatshirt usually fits a 35 x 45 +5 cm mailing bag. Thick or oversized items may need 45 x 55 +5 cm.

When should I use a bubble mailer instead of a poly mailer?

Use a bubble mailer when the item can break, scratch or dent — cosmetics, glass, electronics accessories, books with hard covers. Use a poly mailer for textiles and other soft, unbreakable goods.

Last updated: 25 October 2026 · Packing Envelopes, Istanbul

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