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
Getting size right affects more than just fit:
Reduces waste — right-sized packaging uses less material per order
Prevents damage — a snug fit keeps items from shifting and bending in transit
Controls shipping costs — USPS, UPS, and FedEx apply dimensional weight pricing; oversized mailers add unnecessary fees
Improves presentation — a well-fitted mailer looks intentional and professional
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
- 6″ x 9″ or 7.5″ x 10.5″ — socks, underwear, accessories, scarves
- 9″ x 12″ or 10″ x 13″ — single shirts, blouses, shorts, skirts, up to 5 folded shirts
- 12″ x 15.5″ — sweaters, pairs of jeans, dresses, S/M/L hoodies
- 14.5″ x 19″ — XL/XXL hoodies, coats, bulkier garments
Electronics & Accessories
- 6″ x 9″ — phone cases, charging cables, screen protectors
- 9″ x 12″ — earbuds, wireless chargers, gaming mice
- 12″ x 15.5″ — iPads, e-readers, gaming controllers
- 14″ x 17″ — laptops and larger devices with padding
ℹ Electronics tip: Use anti-static poly mailers or place items in an anti-static bag before sealing.
Books & Media
- 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
Beauty & Cosmetics
- 6″ x 9″ — lipstick, serums, small palettes, samples
- 9″ x 12″ — foundation bottles, skincare sets
- 10″ x 13″ — larger gift sets, multi-product orders
Home & Bedding
- 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.
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-colour branding options, low minimums, fast dispatch. Visit pluspackaging.com to order.
Conclusion: Choosing the Right Poly Mailer Size
Picking the right poly mailer size comes down to three things: the dimensions of your product when packed flat, the weight you need to ship, and the carrier rates you want to avoid. Use the sizing formula in this guide — width + thickness + 1″ for the mailer width, length + thickness + 2″ for the mailer length — and match the result against the size chart to find your fit.
For most e-commerce businesses shipping apparel, the 10″ x 13″ covers the majority of single-item orders, while the 12″ x 15.5″ handles heavier garments and multi-item packs. Stocking just two or three sizes is enough to cover most SKUs efficiently, keep packaging costs down, and ensure every shipment arrives looking professional.
Once you have the right size locked in, the next step is making the packaging work harder for your brand. A plain mailer ships the product; a custom poly mailers ships the brand. Every delivery becomes a touchpoint — and with low minimum orders, it is more accessible than most businesses expect. Browse our full range of custom packaging solutions or explore custom retail bags if you need premium branded packaging for retail or gifting.