Choosing the wrong poly mailer size costs money, oversized mailers inflate dimensional weight fees, while undersized ones burst at the seams. This guide covers every standard poly mailer size, a step-by-step measuring formula, thickness guidance, and size recommendations by product type.
Why Poly Mailer Size Matters
Poly mailing bags are lightweight polyethylene shipping envelopes designed for non-fragile goods. They are water-resistant, tear-resistant, and self-sealing, making them the go-to choice for apparel, accessories, and soft goods shipped through carriers like USPS, UPS, and FedEx.
Size matters for three reasons:
Shipping costs. All three major carriers use dimensional weight pricing. An oversized mailer inflates the billable weight of a package even when the contents are light. Getting the size right keeps you paying for actual weight, not air.
Product protection. A mailer with too much slack lets items shift and fold on themselves in transit. A tight, snug fit holds contents in place and reduces the chance of creasing, bending, or seam failure under load.
Brand presentation. A well-fitted mailer looks considered and intentional when it lands on a customer’s doorstep. An oversized bag that billows around a small item sends a different message and not a good one.
Most ecommerce businesses stock two or three poly mailer sizes to handle the range of products they ship. Stocking the right sizes means you never overpay on postage and never make a customer worry about whether their order survived the journey.
Poly Mailer Size Chart: All Standard Sizes
All dimensions are width x length (flat measurement, excluding the seal flap).
| Size (W x L) | Weight Range | Best For | Typical Use Case |
| 6″ x 9″ | Up to 0.5 lb | Jewelry, phone cases, cables, cosmetics, small accessories | Subscription boxes, beauty samples |
| 7.5″ x 10.5″ | Up to 1 lb | T-shirts (S/M), scarves, socks, small books, underwear | Fashion brands, Etsy sellers |
| 9″ x 12″ | Up to 1.5 lb | Single shirts, blouses, shorts, documents, thin catalogs | Apparel, office supplies |
| 10″ x 13″ | Up to 2 lb | Adult T-shirts/jeans, light jackets, up to 5 folded shirts | Most popular size, general apparel |
| 12″ x 15.5″ | Up to 3 lb | Sweaters, dresses, pairs of jeans, small/med hoodies, iPads | Mid-size fashion brands |
| 14″ x 17″ | Up to 4 lb | Larger clothing, bulkier items, multiple pieces, gaming controllers | Outerwear, multi-item orders |
| 14.5″ x 19″ | Up to 5 lb | XL/XXL hoodies, coats, bedding, multiple garments, large soft goods | Streetwear, home goods |
How to Choose the Right Poly Mailer Size
Poly mailer dimensions are measured flat. But your product has thickness, you need to account for all three dimensions.
Step 1 — Measure your product
- Length (L): the longest side of the folded item
- Width (W): the shorter side
- Thickness (H): how thick the item is once folded for packing
Step 2 — Apply the sizing formula
Minimum mailer width = W + H + 1 inch
Minimum mailer length = L + H + 2 inches
Step 3 — Pick the next size up
Match your calculated minimums against the size chart and choose the nearest size that meets or exceeds both dimensions.
Example: A folded sweatshirt measuring 11″ x 13″ x 2″ needs a mailer at least 14″ wide and 16″ long. The 14.5″ x 19″ is the correct choice from the standard range.
Poly Mailer Thickness Guide
Thickness (measured in mil) determines how much abuse the mailer can absorb in transit.
- 2 mil — light documents, flat items under 0.5 lb
- 2.5 mil — industry standard; ideal for most clothing and soft goods
- 3.0-3.5 mil — heavier garments, items with sharp corners or zippers
- 4-6 mil — packages over 2 lb or items with irregular shapes
USPS minimum thickness: 2 mil for packages up to 5 lb; 4 mil for packages up to 10 lb.
Poly Mailer Sizes by Industry
Different product categories have distinct needs. Use this reference to stock the right sizes for your business.
| Industry | Small Items | Medium Items | Large Items |
| Fashion / Apparel | 7.5″ x 10.5″ | 10″ x 13″ | 14.5″ x 19″ |
| Electronics | 6″ x 9″ | 9″ x 12″ | 12″ x 15.5″ |
| Books & Media | 6″ x 9″ | 9″ x 12″ | 12″ x 15.5″ |
| Beauty & Cosmetics | 6″ x 9″ | 9″ x 12″ | 10″ x 13″ |
| Home & Bedding | 9″ x 12″ | 12″ x 15.5″ | 14.5″ x 19″ |
Fashion & Apparel
Apparel is the most common use case for custom poly mailing bags. The right size depends almost entirely on how bulky the garment is when folded.
- 6″ x 9″ or 7.5″ x 10.5″ — socks, underwear, accessories, scarves, thin belts
- 9″ x 12″ — single shirts, blouses, shorts, skirts, kids clothing
- 10″ x 13″ — adult T-shirts, jeans, light jackets, up to five folded shirts
- 12″ x 15.5″ — sweaters, dresses, pairs of jeans, S/M/L hoodies
- 14.5″ x 19″ — XL/XXL hoodies, coats, bulkier outer layers, multi-item orders
For brands shipping a wide size range, stock the 10″ x 13″ and 12″ x 15.5″ as your two primary sizes. They cover the vast majority of adult garment shipments between them.
If you ship eco-conscious clothing or want a more sustainable option alongside your poly bags, compostable mailers are available in the same core size range and drop in as a direct swap.
Electronics & Accessories
Electronics require a snug fit to prevent movement and reduce the risk of contact damage. For anything with sensitive components, always place items in an anti-static bag before sealing inside the poly mailer.
14″ x 17″ — compact laptops (with sleeve or padding inside)
6″ x 9″ — phone cases, charging cables, screen protectors, small peripherals
9″ x 12″ — earbuds, wireless chargers, small gaming mice, power banks
12″ x 15.5″ — tablets, e-readers, gaming controllers
Books & Media
Books need a size that holds the item flat without allowing it to slide around. A mailer slightly wider than the book with minimal slack on each side is ideal.
- 6″ x 9″ — small paperbacks, cards, thin magazines
- 9″ x 12″ — standard paperbacks, A4 documents, thin catalogs
- 12″ x 15.5″ — hardcovers, textbooks, multiple documents
For customers who prefer a padded option with paper construction, paper padded mailers offer a similar size range with added cushioning and a more premium unboxing feel. For a lightweight paper alternative to poly, paper mailers work well for flat documents and catalogues.
Beauty & Cosmetics
Beauty products often ship in small quantities with high average order values. Right-sizing the mailer keeps the packaging from looking oversized relative to the product inside.
- 6″ x 9″ — lipstick, serums, small palettes, samples
- 9″ x 12″ — foundation bottles, skincare sets
- 10″ x 13″ — larger gift sets, multi-product orders
For fragile cosmetic bottles, consider bubble mailers instead, which add a protective cushioning layer around glass and fragile packaging without the need for extra void fill.
Home & Bedding
Soft home goods compress well and ship efficiently in standard poly mailers up to a point. Beyond a certain volume, an expansion or gusseted mailer is needed.
- 12″ x 15.5″ — pillowcases, hand towels, light linens
- 14.5″ x 19″ — sheets, lightweight blankets, bed sets
ℹ Very bulky items (duvets, pillows) may need gusseted or expansion mailers rather than standard flat poly mailers.
How Poly Mailer Sizes Compare to Other Mailer Types
Poly mailers are not always the right tool for the job. Here is how they compare to the other main mailer formats:
Bubble mailers have a padded inner layer that protects fragile or rigid items during transit. They run slightly thicker than standard poly for the same interior dimensions. Use bubble mailers for glass, hard cases, electronics, and anything that can crack under pressure.
Paper mailers are a paper-based alternative for flat, lightweight items. They are not waterproof, so they work best in controlled shipping environments or when contents are already in protective packaging. They carry a more premium, craft-paper feel for brands that want that aesthetic.
Paper padded mailers combine a paper exterior with a pulp or honeycomb padding layer inside. They are a popular eco-conscious alternative to bubble mailers and work well for small electronics, cosmetics in hard cases, and lightweight products that need moderate protection.
Compostable mailers match standard poly mailer dimensions exactly and are the direct swap for brands reducing their plastic use. They ship the same way, seal the same way, and carry branding just as well.
If you are deciding which format is right for your products, the key question is protection level needed versus cost per unit.
Frequently Asked Questions
What is the most popular poly mailer size?
The 10″ x 13″ is the industry standard and the single most widely used size. It fits adult T-shirts, jeans, light jackets, and up to five folded shirts. The 12″ x 15.5″ is a close second for clothing brands shipping heavier or bulkier garments.
How do poly mailer dimensions work?
In standard notation (e.g. 10″ x 13″), the first number is always the width and the second is the length. So a 10″ x 13″ mailer is 10 inches across and 13 inches tall.
What size poly mailer fits a hoodie?
A 12″ x 15.5″ fits most S, M, and L hoodies when folded flat. For XL and XXL hoodies, use a 14.5″ x 19″. Very thick oversized hoodies may need a 15″ x 20″ or expansion-style mailer.
What size poly mailer for T-shirts?
One adult T-shirt typically fits in a 10″ x 13″. For multiple shirts or larger sizes, move up to 12″ x 15.5″. A single kids shirt fits in a 9″ x 12″.
Can I use one poly mailer size for all my products?
Not recommended. Oversized mailers on small items increase shipping costs through dimensional weight pricing. Undersized mailers risk seam failure. Most e-commerce businesses keep 2-3 sizes on hand to cover their product range efficiently.
What size poly mailer fits an A4 document?
An A4 sheet is approximately 8.3″ x 11.7″. A 9″ x 12″ poly mailer is the standard choice and provides a snug, professional fit.
Are poly mailer dimensions measured with or without the seal flap?
Dimensions are measured flat, excluding the seal flap. The adhesive flap typically adds 1.5-2 inches to the total length but folds over to seal and does not add to usable internal space. Always calculate your product fit against the stated dimensions, not the total bag length.
Shop poly mailers at Plus Packaging: All standard sizes from 6″ x 9″ to 14.5″ x 19″, full-color branding options, low minimums, fast dispatch. Visit pluspackaging.com to order.
Conclusion
Choosing the right poly mailer size comes down to three things: the dimensions of your product when packed flat, the weight you are shipping, and the carrier rates you want to avoid. Use the formula above (width + thickness + 1″ for mailer width; length + thickness + 2″ for mailer length) and match the result against the size chart to find your fit.
For most ecommerce businesses shipping apparel, the 10″ x 13″ handles the majority of single-item orders. The 12″ x 15.5″ covers heavier garments and multi-item packs. Two sizes between them handle most SKUs without overspending on packaging.
Once you have the size locked in, the next step is making the packaging work harder for your brand. A plain poly bag ships the product. Custom poly mailing bags ship the brand. Every delivery becomes a touchpoint with your customer, and with low minimum order quantities, branded packaging is more accessible than most businesses expect.
If your products call for something different, explore the full range: paper mailers for flat lightweight goods, bubble mailers for fragile items, paper padded mailers for a sustainable cushioned option, and compostable mailers for brands reducing their plastic footprint.