Picking the wrong size costs you twice. Go too big and you are paying for air and shipping tape you did not need. Go too small and the seams split before the package even reaches the truck. This guide walks through every standard size Pro Supply Global stocks, the formula for measuring your product, mil thickness, current shipping cost rules, and how poly mailer shipping bags compare to other mailer types, so you only have to size a package once.
What Size Poly Mailer Do I Need?
For most single-item apparel orders, a 10x13 poly mailer is the standard pick. It fits an adult T-shirt, a pair of jeans, or a light jacket without excess slack. If your catalog spans smaller accessories up to bulkier multi-item orders, stock two or three sizes rather than one:
- Small items: 6x9
- Single garments: 10x13
- Hoodies and multi-item packs: 12x15
- Bulkier soft goods: 18x18
- Coats, blankets, and large linens: 19x24
What Is a Poly Mailer?
A poly mailer is a lightweight shipping envelope made from polyethylene film. It is water-resistant, tear-resistant, and closes with a self-sealing adhesive strip, so no extra tape is needed. Poly mailers are built for non-fragile items such as clothing, soft goods, and accessories, where a rigid box would add unnecessary weight and cost. They cannot cushion glass, electronics with sensitive internal parts, or anything that can be crushed, which is why size and material choice both matters more than they would with a box.
Poly Mailer Size Chart: What Are the Standard Sizes?
All dimensions below are flat measurements and exclude the seal flap, which typically adds another 1.5 to 2 inches to the total length but does not count toward usable space.
| Size (W × L) |
Weight Range |
Best For |
| 6" × 9" |
Up to 0.5 lb |
Jewelry, phone accessories, small cosmetics, socks |
| 10" × 13" |
Up to 2 lb |
Single adult T-shirt, jeans, light jacket, up to five folded shirts |
| 12" × 15" |
Up to 3 lb |
Hoodies, sweaters, multi-item apparel orders |
| 18" × 18" |
Up to 4 lb |
Bulkier soft goods, square or multi-item orders |
| 19" × 24" |
Up to 5 lb |
Coats, blankets, bedding, large linens |
These five sizes cover the full range Pro Supply Global carries, so whatever you land on in this guide, you can order it directly from the matching collection.
Why Does Poly Mailer Size Matter?
Getting the size right affects three things at once.
Shipping cost. An oversized mailer wastes material and, on larger multi-item shipments, can push a package closer to size thresholds that trigger higher carrier pricing. A snug fit keeps you paying for the product, not the packaging around it.
Product protection. Too much slack lets an item shift and fold on itself in transit, which increases the chance of creasing or seam failure under pressure. A properly sized mailer holds the product in place without straining the seal.
Brand presentation. A mailer that fits looks intentional when it arrives at a customer's door. An oversized bag billowing around a small item does not send the same impression, no matter how good the product inside is.
Most sellers stock two or three sizes to cover their catalog, which keeps all three of these in balance without overcomplicating fulfillment.
How to Measure a Poly Mailer?
Before matching a product to a size, measure it the way it will actually sit inside the bag:
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Lay the product flat. Fold it the way it would sit inside the mailer before taking any measurements.
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Width: the shorter side, measured across the flattened product
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Length: the longest side of the item once it is folded flat
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Thickness: how thick the item is once folded, including any tissue paper or inner packaging
A soft, compressible item like a folded hoodie behaves differently from a rigid one. If your product is puffy or bulky, such as a packed sweater or a down vest, add extra allowance beyond the flat measurement, since it will expand once inside the mailer.
Keep in mind that the size printed on a poly mailer is its external flat dimension. The usable interior space is slightly smaller once you account for the material itself and the sealed edges, so a product measuring right at the edge of a size's stated dimensions may still fit tight. When a product is close to a size boundary, sizing up avoids a snug fit that strains the seal.
For a deeper walkthrough with worked examples and step by step measuring tips, our earlier guide, How to Calculate the Size of Poly Mailer for Shipping, covers the process in more detail and remains one of our most visited posts.
What Is the Formula for Poly Mailer Size?
Once you have your product's length, width, and thickness, apply this formula:
Mailer width = product width + product thickness + 1 inch
Mailer length = product length + product thickness + 2 inches
Example: A folded hoodie measuring 11" wide x 13" long x 2" thick needs a mailer at least 14" wide and 16" long. The nearest match in Pro Supply Global's range is the 12x15, which fits most S, M, and L hoodies, or the 18x18 for a bulkier fit with room to spare.
Match your calculated minimums against the size chart above and choose the nearest size that meets or exceeds both numbers.
What Size Poly Mailer Fits My Product?
| Category |
Small |
Medium |
Large |
| Fashion and apparel |
6×9 |
10×13 |
12×15 / 18×18 |
| Electronics and accessories |
6×9 |
10×13 |
12×15 |
| Beauty and cosmetics |
6×9 |
10×13 |
12×15 |
| Home and soft goods |
10×13 |
12×15 / 18×18 |
19×24 |
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Fashion and Apparel
Apparel is the most common use case for poly mailer bags. Socks, belts, and small accessories fit a 6x9. A single T-shirt or pair of jeans fits a 10x13, the most widely used size for single-garment orders. If branding matters for your packaging, see our roundup of Most Popular 10x13 Poly Mailer Designs for Small Businesses for design ideas at this size. Hoodies and sweaters need the extra room of a 12x15. For bulkier multi-item orders or winter layers, the 18x18 or 19x24 gives enough space without the item straining the seal.
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Electronics and Accessories
Small peripherals, cables, and phone accessories fit comfortably in a 6x9. Always place sensitive components in an anti-static bag first, since the poly mailer itself provides no static protection.
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Beauty and Cosmetics
Individual items and samples fit a 6x9. Multi-product gift sets or bundled orders are better suited to a 10x13, which gives enough room without the bag looking oversized relative to the product.
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Home and Soft Goods
Towels and light linens fit a 12x15 or 18x18. Bedding, blankets, and larger soft goods need the 19x24 to avoid overstuffing the bag.
Across every category, Pro Supply Global's poly mailer designs let you match the size to the product without giving up on branding. A printed mailer protects exactly the same as a plain one, the design is purely a branding layer on top.
How Can You Add Extra Protection Inside a Poly Mailer?
A correctly sized mailer does not have to be the only layer between the product and the outside world. A few simple additions add protection or presentation without changing the size you order:
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Tissue paper wrapped around folded items adds a premium unboxing feel and a small amount of cushioning
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An inner poly bag keeps folded clothing dry and organized if the outer mailer is opened before delivery
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A flat insert or piece of cardboard helps protect prints, photos, or documents from bending inside the mailer
None of these changes which size mailer you need. Account for their thickness when measuring your product, since tissue paper and inserts add a small amount of depth that factors into the sizing formula above.
What Mil Thickness Should I Use?
Thickness, measured in mil, determines how much a mailer can absorb during transit:
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2 mil: light, flat items under 0.5 lb
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2.5 mil: the standard for most clothing and soft goods
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3 to 3.5 mil: heavier garments, zippers, or items with sharp corners
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4 to 6 mil: packages over 2 lb or irregular shapes
Thickness and size are independent decisions. A correctly sized mailer in too thin a material will still tear on a sharp buckle or zipper, so size the bag first, then confirm the mil matches what is going inside it.
This is also where eco friendly poly mailers and biodegradable mailers fit in. Pro Supply Global's biodegradable collection covers the same size range as the standard poly mailer line, so switching to a lower-impact material does not mean compromising on fit or moving to a size you do not already stock.
How Does Poly Mailer Size Affect Shipping Cost?
Carriers price bulky packages using dimensional (DIM) weight, which charges based on the space a package occupies rather than its actual weight. As of July 2026, USPS changed how this is calculated: the divisor used to convert volume into billable weight dropped from 166 to 139, and any fractional inch in a package's dimensions now rounds up instead of down. Together, these changes raise billable weight by roughly 19 percent on affected packages.
The rule only applies to packages over 1 cubic foot (1,728 cubic inches). This is where poly mailers have a built-in advantage over boxes: because a poly mailer conforms to the shape of the product instead of holding a fixed rigid volume, most poly mailer shipments stay under that threshold entirely and are billed at actual weight, not DIM weight. Right-sizing the mailer, rather than reaching for the next size up "just in case," is now worth more in real shipping dollars than it was before this rule change.
When Should You Use a Poly Mailer, and When Should You Not?
Poly mailers work best for products that are non-fragile, reasonably flat, and can be folded or compressed without damage. That covers most clothing, textiles, soft accessories, and lightweight non-breakable goods.
They are not the right choice for everything. Fragile items such as glass, ceramics, or delicate electronics need rigid protection a poly mailer cannot provide. Very bulky or rigid items that do not conform to a flexible bag risk stretching or tearing the material. High-value items that call for extra security are usually better suited to a box.
If a product falls into any of those categories, a corrugated box or a padded rigid mailer is the safer packaging choice, regardless of how well you size the poly mailer.
How Do Poly Mailers Compare to Other Mailer Types?
Bubble mailers add a padded interior layer, which makes them bulkier and slightly more expensive than standard poly, but far better suited to fragile, hard cased, or electronic items. If you are choosing between styles, Pro Supply Global's bubble mailer design options give the same branding flexibility as printed poly mailers while adding that protective cushioning layer. For help matching a size to what you are shipping, see our guide on How to Choose the Right Bubble Mailer Size for Shipping.
Paper mailers are not waterproof and work best for flat, lightweight, non-fragile items already protected inside their own packaging.
Biodegradable mailers match the standard poly mailer size chart exactly, seal the same way, and print the same way, making them a direct swap for brands looking to reduce plastic use without changing anything about how the packaging is used day to day.
The decision comes down to one question: how much protection does the product need versus how much you are willing to spend per unit.
What Are the Most Common Poly Mailer Sizing Mistakes?
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Oversizing "just in case." This wastes material and, under the new DIM weight rules, can push a package closer to the 1 cubic foot threshold sooner than expected.
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Undersizing or overstuffing. A mailer under strain is far more likely to split at the seam in transit.
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Ignoring the seal flap. The flap adds length to the total bag but not to usable space, so always compare product length against the stated flat dimensions, not the full bag length.
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Treating thickness as fixed. A well sized bag in too thin a mil will still fail on sharp corners, zippers, or heavier items.
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Assuming printed mailers are weaker. Print does not affect strength or protection. Poly mailers with designs perform identically to plain ones in the same size and mil.
Which Poly Mailer Size Should You Choose?
Getting poly mailer size right comes down to three numbers: your product's measured dimensions, the formula above, and the nearest size in the chart that covers both. For most apparel sellers, the 10x13 and 12x15 handle the bulk of single item and multi item orders between them, with the 6x9 covering small accessories and the 18x18 or 19x24 covering bulkier or seasonal items.
Browse Pro Supply Global's full range, including standard, designer, and biodegradable poly mailer shipping bags in every size covered in this guide, to find the exact fit for your next shipment.
