Poly mailers come in seven common sizes, from 6 × 9 inches up to 19 × 24 inches, with the right pick depending on your item’s dimensions.
For the full breakdown, see our best 6X9 Poly Mailers guide.
If you sell online or ship regularly, choosing the wrong poly mailer size wastes money on postage and risks damage in transit. The good news is that a handful of standard US-market sizes cover nearly every e-commerce need, from a single pair of socks to a bulky winter coat.
Standard Poly Mailer Sizes and Their Best Uses
There is no single universal standard size for poly mailers, but packaging suppliers consistently stock the same core set. The table below shows the most common poly mailer dimensions and what each one fits best.
| Mailer Size | Best For |
|---|---|
| 6 × 9 in | Jewelry, phone cases, socks, small accessories |
| 7.5 × 10.5 in | Thin clothing, kids’ shirts, small apparel |
| 9 × 12 in | Adult T-shirts, documents, thin bundles |
| 10 × 13 in | Leggings, shorts, books, multiple small items |
| 12 × 15.5 in | Hoodies, sweaters, jeans, several garments |
| 14.5 × 19 in | Coats, bulk soft goods, multi-item orders |
| 19 × 24 in | Bulky items and larger shipments |
Some suppliers also list a 24 × 36 in option, but this is a custom or oversize choice rather than a universal standard. Stick with the common sizes above unless you regularly ship something unusually large.
How To Pick The Right Poly Mailer Size
Choosing the right poly mailer size comes down to one rule: pick a bag slightly larger than your item, not one that fits it exactly. The usable interior space of a poly mailer is smaller than its exterior dimensions because the side seams and adhesive flap take up room.
Packaging suppliers offer two practical formulas for adding that buffer. One approach is to add roughly 1/2 inch to 1 inch of extra space on all sides of your item. Another is to add about 1 inch to the width and 2 inches to the length to account for the side seals and the flap. Either method works; the important thing is to measure your item’s length, width, and depth before you buy.
Oversized mailers are a common mistake.
Do Poly Mailer Sizes Match USPS Mail Classes?
Poly mailer sizes do not have official USPS size classifications, but supplier charts commonly pair certain dimensions with specific mail classes based on weight. These are practical recommendations from packaging companies, not postal regulations.
In the typical supplier guidance, 6 × 9 and 9 × 12 bags suit lighter First-Class Package shipments. A 10 × 13 mailer works for First-Class or Priority Mail depending on weight. The 12 × 15.5 size and larger bags generally pair with Priority Mail. GoShippo’s poly mailer guide walks through these weight and class combinations in more detail.
FAQs
What is the most common poly mailer size?
The 10 × 13 inch poly mailer is the most frequently cited standard for e-commerce because it fits common items like leggings, shorts, books, and multiple small products. The 9 × 12 inch size is nearly as popular for adult T-shirts and thin garments.
How much bigger should a poly mailer be than the item?
Add about 1/2 inch to 1 inch of extra space on all sides of your item, or add roughly 1 inch to the width and 2 inches to the length. The extra room accounts for side seams, the adhesive flap, and the fact that interior space is smaller than exterior dimensions.
Can one poly mailer size fit most products?
No single poly mailer works for every product. A 6 × 9 size fits small accessories, while a 14.5 × 19 size is needed for coats and bulk orders. Most sellers stock two or three sizes to cover the range of items they ship without paying for oversized bags.
References & Sources
- GoShippo. “What is a Poly Mailer?” Explains poly mailer types and how sizes pair with USPS mail classes.