Quick answer: A custom poly mailer is a lightweight, water-resistant plastic shipping bag printed with your brand, made in the size and film you choose. Most are 2 to 3 mil polyethylene with a self-seal strip. Popular sizes run from 6 × 9 in to 24 × 24 in; 10 × 13 in fits most T-shirts, and 12 × 15.5 in or 14.5 × 19 in fits hoodies.
Key facts at a glance
- Material: polyethylene (resin code #4 LDPE is common), often co-extruded white outside and dark inside for privacy
- Thickness: usually 2 to 3 mil; 1 mil = 0.001 in (25.4 microns)
- Common sizes: 6 × 9, 7.5 × 10.5, 9 × 12, 10 × 13, 12 × 15.5, 14.5 × 19, 19 × 24 and 24 × 24 in
- Hoodies: 12 × 15.5 in for light and medium hoodies, 14.5 × 19 in for heavy, XL or two hoodies
- Sizing rule: width = item width + thickness + about 1 in; length = item length + thickness + about 2 in
- USPS cubic pricing: soft packs are priced by length + width, up to 36 in
- Recycling: poly mailers go to plastic film store drop-off, not most curbside bins
In this guide
- What a custom poly mailer is
- Poly mailer size chart
- How to choose the right size
- What size poly mailer for hoodies
- Materials and thickness
- Closures and features
- Branding and printing options
- Poly mailers and shipping costs
- Poly mailer vs bubble mailer vs mailer box
- Sustainability and recycling
- How to order custom poly mailers
- Common mistakes
- Frequently asked questions
- Sources
What Is a Custom Poly Mailer?
A custom poly mailer is a flat, self-sealing shipping bag made from polyethylene film and printed with your logo, colors or message. It replaces a box for soft, non-fragile products such as clothing, textiles and accessories. Poly mailers are light, flexible and water-resistant, take up little storage space and cost less to ship than a box of the same size.
A branded poly mailer turns a plain shipping bag into part of your brand: it is the first thing customers see when an online order arrives. For brands that also use boxes, poly mailers often sit alongside printed mailer boxes for heavier or more premium orders.
| Best For | Not Ideal For |
|---|---|
| T-shirts, hoodies, leggings and sweaters | Glass, ceramics and other fragile items |
| Swimwear, socks, underwear and scarves | Products that crush, such as cosmetics in thin cartons |
| Soft accessories, bags and textiles | Sharp or pointed items that can puncture film |
| Boxed items that only need an outer layer | Gift orders where a premium unboxing matters most |
Poly Mailer Size Chart
Poly mailer dimensions are listed as width × length in inches, measured flat on the outside, usually not counting the seal flap. The space you can actually use is a little smaller once the bag fills: Sticker Mule, for example, lists a 10 × 13 in mailer with 9.5 × 13 in of internal space (Sticker Mule).
| Size (in) | Size (cm) | Typical Uses |
|---|---|---|
| 6 × 9 | 15 × 23 | Jewelry, socks, small accessories, samples |
| 7.5 × 10.5 | 19 × 27 | Underwear, scarves, kids’ tees, small cosmetics in pouches |
| 9 × 12 | 23 × 30 | One folded T-shirt, leggings, shorts, books |
| 10 × 13 | 25 × 33 | Adult T-shirts, blouses, dresses, light sweaters |
| 12 × 15.5 | 30 × 39 | Hoodies and sweatshirts (S to L), jeans, two or three tees |
| 14 × 17 | 36 × 43 | Sweatshirts, light jackets, several garments |
| 14.5 × 19 | 37 × 48 | Heavy or XL hoodies, jackets, two hoodies, shoe boxes |
| 19 × 24 | 48 × 61 | Coats, bedding, bulk apparel orders |
| 24 × 24 | 61 × 61 | Comforters, large coats, oversized soft goods |
These are common stock sizes, used across suppliers such as AMZ Prep and UPrinting; centimeters are converted and rounded. Custom poly mailers can also be made to any size between standard sizes.
How to Choose the Right Poly Mailer Size
A flat bag loses length and width as it wraps around a thick item, so measure the folded product, not just its flat footprint.
- Fold the item the way you will ship it, with any tissue, card or inner bag.
- Measure its width, length and thickness at the widest points.
- Calculate width: item width + item thickness + about 1 in.
- Calculate length: item length + item thickness + about 2 in, leaving room to seal the flap.
- Pick the next size up on the size chart if you fall between sizes.
- Pack-test a sample before ordering a full run of printed mailers.
Example: a folded T-shirt of 8 × 10 × 1 in needs about 8 + 1 + 1 = 10 in wide and 10 + 1 + 2 = 13 in long, so a 10 × 13 in poly mailer is the right fit. This rule of thumb follows AMZ Prep’s sizing formula; real garments vary, so always test with your own products. For boxes, see this guide to choosing custom box sizes.
What Size Poly Mailer for Hoodies?
Hoodies are thicker than tees, so they need a larger mailer than their flat size suggests. Here is what size poly mailer for hoodies works in most cases:
| Hoodie | Recommended Mailer | Film |
|---|---|---|
| Lightweight hoodie or kids’ hoodie | 10 × 13 in (tight) or 12 × 15.5 in | 2.5 mil |
| Standard adult hoodie (S to L) | 12 × 15.5 in | 2.5 to 3 mil |
| Heavyweight, fleece, zip-up or XL to XXL | 14.5 × 19 in | 3 mil |
| Two medium hoodies | 14.5 × 19 in | 3 mil |
| Hoodie plus joggers set | 14.5 × 19 in or 19 × 24 in | 3 mil |
Sticker Mule rates its 10 × 13 in mailer for one medium hoodie and its 14.5 × 19 in mailer for two medium hoodies (Sticker Mule), and AMZ Prep recommends 12 × 15.5 in for S to L hoodies and 14.5 × 19 in for XL to XXL. If you sell custom apparel boxes for gift orders, a poly mailer of the same branding works well for everyday orders.
Poly Mailer Materials and Thickness
Most poly mailers are low-density polyethylene (LDPE, resin code #4) or blends, often co-extruded in two layers: a white or colored outside that takes print well and a gray, silver or black inside that hides the contents. Commercial spec sheets describe these as opaque co-extruded mailers with a tamper-evident self-seal strip (WebstaurantStore spec sheet).
| Film Type | What It Is | Good to Know |
|---|---|---|
| Virgin LDPE | New polyethylene film | Consistent strength and print quality |
| Recycled content (PCR or PIR) | Film with post-consumer or post-industrial recycled plastic | Lowers new plastic use; ask for the recycled percentage and certification |
| Co-extruded (co-ex) | Two or more layers made together | Opaque inside for privacy, smooth print surface outside |
| Compostable film | Bio-based or compostable polymer blends | Only “compostable” if it breaks down in a real composting system; check certifications and claims |
| Metallic or holographic | Film with a metallic finish | Strong shelf appeal; usually harder to recycle |
Poly Mailer Thickness (Mil)
Film thickness is measured in mils: 1 mil equals 0.001 in, or 25.4 microns. Sticker Mule’s custom mailers, for example, are 2.5 to 3 mil (Sticker Mule).
| Thickness | Best For |
|---|---|
| 1.5 to 2 mil | Light, flat items such as socks, scarves and samples |
| 2.5 mil | Standard for T-shirts and most clothing |
| 3 to 3.5 mil | Hoodies, denim, zippers and heavier garments |
| 4 mil and up | Heavy, bulky or irregular items |
Thickness guidance follows common supplier recommendations such as AMZ Prep. Thicker film resists tears and punctures better but adds weight and cost. For items that need cushioning, choose a padded mailer or a box instead.
Poly Mailer Closures and Features
- Self-seal adhesive strip: a peel-and-seal strip under a release liner; most are permanent and tamper-evident, so the bag tears if someone tries to open it.
- Dual adhesive (returnable): a second strip lets customers reuse the mailer for returns, which helps apparel brands with high return rates.
- Tear strip: a perforated line that opens the bag cleanly without scissors.
- Gusseted or expandable: pleated sides or bottom give extra depth for bulky items.
- Handles or window pockets: carry handles for retail or a clear pocket for packing slips.
Protect the garment inside with a clear inner bag; clear cellophane bags keep items clean and presentable.
Branding and Printing Options for Custom Poly Mailers
Custom printed poly mailer bags can carry anything from a single-color logo to full-coverage artwork. The print method affects cost, colors and minimum order size.
| Print Method | How It Works | Best For |
|---|---|---|
| Flexographic | Flexible printing plates, usually one plate per ink color | Logos and spot colors on larger runs; not ideal for photos or gradients |
| Rotogravure | Graphics engraved into printing cylinders | High-volume runs with detailed, consistent artwork |
| Digital | Prints directly from the file, no plates | Short runs, full-color designs and frequent design changes |
Print method details follow Industrial Packaging, which notes flexo is low-cost and fast but can show banding in gradients and is not suited to photographic images.
Branded Poly Mailer Design Tips
- Keep it bold: a large logo, one or two brand colors and a short message read well on film.
- Print both sides: the shipping label covers part of one side, so put key branding where the label won’t go.
- Leave a label zone: plan a clear area for a 4 × 6 in shipping label.
- Avoid flaps and folds: EcoEnclose, for example, does not print on flaps or folds and allows up to 1/4 in of print movement (EcoEnclose).
- Size small text carefully: EcoEnclose sets a minimum of 12 pt type (14 pt reversed out) and 1.25 × 1.25 in for QR codes on flexo-printed mailers.
- Use vector artwork: AI or PDF with outlined fonts, and Pantone colors for exact brand matching.
- Add a message inside: inside printing adds a reveal when customers open the bag.
Match colors across your packaging with the CMYK color converter, preview designs with the 3D packaging mockup generator, and add branded packaging stickers or thank-you cards inside for a fuller unboxing. For layout ideas across all your packaging, see these steps for custom packaging design.
How Poly Mailers Affect Shipping Costs
Poly mailers weigh very little: Sticker Mule lists its large 14.5 × 19 in mailer at 0.4 oz. Size matters as much as weight, because carriers also charge by dimensions.
- Dimensional weight: UPS, FedEx and, from July 12, 2026, USPS use a DIM divisor of 139. USPS applies DIM pricing only to packages over one cubic foot (1,728 cubic inches) (DCL Logistics), so most filled poly mailers pay by actual weight with USPS.
- USPS cubic pricing for soft packs: for Priority Mail Cubic, soft packs are priced by length plus width of the original packaging, rounded down to the nearest 1/4 in, up to 36 in total, 20 lb and a longest side of 22 in (USPS DMM 223).
| Mailer Size (in) | Length + Width | USPS Soft Pack Cubic Tier |
|---|---|---|
| 6 × 9 | 15 in | 0.10 |
| 7.5 × 10.5 | 18 in | 0.10 |
| 9 × 12 | 21 in | 0.10 |
| 10 × 13 | 23 in | 0.20 |
| 12 × 15.5 | 27.5 in | 0.30 |
| 14 × 17 | 31 in | 0.30 |
| 14.5 × 19 | 33.5 in | 0.40 |
| 19 × 24 | 43 in | Not eligible (over 36 in and 22 in) |
Tiers are based on the listed bag sizes; measure your actual mailer, including any flap that adds length, before choosing a tier. Smaller mailers fall into lower tiers, which is another reason to right-size. Check box shipments with the dimensional weight calculator.
Poly Mailer vs Bubble Mailer vs Mailer Box
| Factor | Poly Mailer | Bubble (Padded) Mailer | Mailer Box |
|---|---|---|---|
| Protection | Water and scuff resistance only | Light cushioning | Crush and impact protection |
| Weight | Lightest | Light | Heaviest |
| Storage | Very compact | Compact | Ships flat, takes more space |
| Best for | Clothing and soft goods | Small items that need light padding | Fragile, premium or gift orders |
| Unboxing | Printed bag, quick to open | Practical | Premium, with inside printing and inserts |
| Recycling | Plastic film drop-off | Depends on construction; mixed materials are harder | Paper; widely curbside recyclable |
For orders that need structure, compare kraft mailer boxes or corrugated shipping boxes. For a full overview of formats, read the complete custom packaging guide.
Sustainability and Recycling
- Recycling: poly mailers are plastic film. Most curbside programs do not accept #4 film, so they usually go to store drop-off bins with plastic bags. Sticker Mule notes that #4 is “often not accepted at curbside recycling programs,” and mailer maker Pac Worldwide directs customers to grocery store film drop-off bins (Pac Worldwide).
- Print the right instructions: a How2Recycle “Store Drop-Off” style instruction tells customers where the bag goes.
- Use recycled content: PCR film reduces new plastic and is a claim you can verify with certificates.
- Be careful with claims: under the FTC Green Guides, an unqualified “recyclable” claim needs recycling access for at least 60% of consumers or communities (Kelley Drye summary), and “compostable” means it breaks down into usable compost in a safe and timely manner.
- Watch California: California’s SB 343 limits recycling symbols and claims to materials that meet its collection and sorting thresholds. Its October 4, 2026 compliance date was paused when a federal court granted a preliminary injunction on July 14, 2026 (Davis Wright Tremaine). Check the latest status before printing recycling symbols for California.
- Right-size and reuse: the smallest mailer that fits uses the least film, and dual-adhesive mailers get a second use for returns.
Compare eco-friendly packaging options if paper-based mailers suit your brand better.
How to Order Custom Poly Mailers
- List your products and measure each folded item, including inner bags and inserts.
- Choose sizes: most apparel brands need two or three sizes, such as 10 × 13, 12 × 15.5 and 14.5 × 19 in.
- Choose film: thickness, color, recycled content and opacity.
- Choose features: single or dual adhesive, tear strip, gusset or handles.
- Prepare artwork on the supplier’s template: vector files, Pantone colors, label zone and no print on flaps.
- Approve a proof and, for a first order, test a sample with your real products.
- Plan quantities by size based on your order mix, so you don’t run out of your best-selling size.
Get started with BoxNovo’s custom poly mailers, browse all custom packaging bags, or check a budget range with the instant price estimate tool.
Common Custom Poly Mailer Mistakes
| Mistake | Fix |
|---|---|
| Measuring the flat garment, not the folded item | Add the item’s thickness to width and length |
| Ordering one size for every product | Stock two or three sizes based on your order mix |
| Film too thin for hoodies or denim | Use 2.5 to 3 mil or thicker for heavier garments |
| No space for the shipping label | Leave a clear 4 × 6 in label zone in the artwork |
| Printing photos with flexo | Use bold logos and spot colors, or digital printing for full color |
| Shipping fragile items in a poly mailer | Use a padded mailer or a box |
| Unqualified “eco” or “biodegradable” claims | Make specific claims you can prove, with correct recycling instructions |
Frequently Asked Questions
What is a custom poly mailer?
A plastic shipping bag made from polyethylene film, printed with your brand and made in the size, color and thickness you choose.
What are standard poly mailer dimensions?
Common sizes are 6 × 9, 7.5 × 10.5, 9 × 12, 10 × 13, 12 × 15.5, 14 × 17, 14.5 × 19, 19 × 24 and 24 × 24 in, listed as width × length.
What size poly mailer for hoodies?
12 × 15.5 in for most S to L hoodies, and 14.5 × 19 in for heavyweight, XL or zip-up hoodies, or two hoodies.
What size poly mailer for a T-shirt?
10 × 13 in fits most folded adult T-shirts; 9 × 12 in fits a single thin or kids’ tee.
How do I measure for a poly mailer?
Measure the folded item. Mailer width should be about item width + thickness + 1 in, and length about item length + thickness + 2 in.
How thick should a poly mailer be?
2.5 mil suits most clothing, 3 mil or more suits hoodies, denim and heavier items. 1 mil equals 0.001 in.
Are poly mailer sizes inside or outside dimensions?
Usually outside flat dimensions without the flap. Usable space is slightly smaller once the item has thickness.
Can custom printed poly mailer bags be printed on both sides?
Yes. Most suppliers offer one- or two-sided printing, and some offer inside printing.
What is the best print method for a branded poly mailer?
Flexo suits logos and spot colors on larger runs, rotogravure suits high-volume detailed artwork, and digital suits short full-color runs.
Are poly mailers waterproof?
They are water-resistant and protect contents from rain and dirt in transit, but they are not sealed for submersion.
Are poly mailers recyclable?
Usually through plastic film store drop-off, not curbside. Check local rules and print clear recycling instructions on the bag.
Are poly mailers cheaper to ship than boxes?
Usually, because they are lighter and smaller. USPS bills most filled poly mailers by actual weight, and soft packs qualify for cubic pricing by length plus width.
Can poly mailers be reused for returns?
Yes, if they have a second adhesive strip. Dual-adhesive mailers let customers reseal the same bag.
When should I use a box instead of a poly mailer?
For fragile, crushable or premium gift orders, where a box gives protection and a better unboxing.
Final Takeaway
A custom poly mailer is the lightest, most cost-effective way to ship clothing and soft goods with your brand on the outside. Measure the folded product, add its thickness to choose the size, pick 2.5 to 3 mil film, plan a clear label zone and keep your artwork bold. Most apparel brands need just two or three sizes, with 12 × 15.5 in or 14.5 × 19 in covering hoodies.
Ready to design yours? Request a mailer quote with your sizes, quantities and artwork.
Sources
- Sticker Mule: poly mailer specs and FAQs
- AMZ Prep: poly mailer sizes, thickness and sizing formula
- UPrinting: poly mailer size guide
- WebstaurantStore: co-extruded poly mailer spec sheet
- Industrial Packaging: printing methods for flexible packaging
- EcoEnclose: custom mailer artwork guidelines
- USPS DMM 223: Priority Mail Cubic soft packs
- DCL Logistics: USPS DIM weight changes, July 2026
- Pac Worldwide: how to recycle poly mailers
- Kelley Drye: FTC Green Guides summary
- Davis Wright Tremaine: SB 343 injunction
