What we typed
Queen size bed sheet set folded into a 19x24 in poly mailer
Naming the bag size in the product line lets the estimator size the mailer instead of guessing at a box.
Packing
Shipping bag dimensions: a sizing chart
Poly mailers cluster around six common flat sizes, and picking the right one is mostly about matching the bag to what has to fold inside it without straining a seam. The chart below lists the sizes, and the worked example is a queen sheet set in the largest of them, quoted $11.98 on UPS Ground on 2026-08-19.
Live parcel ratesRule cited and datedTracking included
Sized to the item
A 19 × 24 in mailer at 4 lb, priced 2026-08-19.
Six sizes cover most of what ships in a bag
These are the flat sizes, seam to seam, that show up across most mailer suppliers. Individual brands run a fraction of an inch either way, so check the listing before ordering in bulk.
| Size | Typical use |
|---|---|
| 6 × 9 in | A single small item: jewelry, a phone case, a few sheets of stickers |
| 9 × 12 in | A paperback book, a t-shirt, small accessories bundled together |
| 10 × 13 in | Two to three folded t-shirts, a light jacket, a small stack of documents |
| 12 × 15.5 in | A folded hoodie, a pair of shoes without their box, a stack of several garments |
| 14.5 × 19 in | Bundled multi-item orders, a light blanket, bedding for a twin or full bed |
| 19 × 24 in | A pillow, a folded comforter or queen sheet set, several garments packed together |
Bag size sets what fits; weight sets most of the price. A mailer stuffed thick enough to go round instead of flat starts behaving like a box for billing purposes, which is the rule covered next.
A real quote: bedding in the largest standard mailer
On 2026-08-19 we typed “queen size bed sheet set folded into a 19x24 in poly mailer” into the SMKlog calculator, Berkeley Heights, NJ 07922 to Detroit, MI 48201. What follows is the raw output.
Packed size it returned
19 × 24 × 3 in
48 × 61 × 8 cm
Packed weight 4 lb (1.8 kg).
Route
Berkeley Heights, NJ 07922
to Detroit, MI 48201
Real ZIPs, rated at request time.
| Carrier | Service | Price | Transit |
|---|---|---|---|
| UPS | Ground | $11.98 | 4-5 business days |
| UPS | Ground Saver | $12.77 | 4-5 business days |
| USPS | Ground Advantage | $13.42 | 4-5 business days |
| UPS | 3 Day Select | $17.48 | 4-5 business days |
| FedEx | Smart Post | $19.88 | 5-6 business days |
Cheapest here was UPS Ground at $11.98. A folded queen sheet set at 4 lb stays well under the one-cubic-foot dimensional weight line covered below, so this mailer bills on its scale weight, not its size.
When a bag starts billing like a box
USPS's own mail manual, read 2026-08-19, sets the line at one cubic foot: “Postage for parcels addressed for delivery to Zones 1-9 and exceeding 1 cubic foot (1,728 cubic inches) is based on the actual weight or the dimensional weight...whichever is greater.” For a rectangular parcel that dimensional figure is length times width times height divided by 139, rounded up.
Flat mailers stay clear
A 19 × 24 in bag packed flat to 3 in deep comes to about 1,368 cubic inches, under the 1,728 line. Most bags in the chart above never approach it unless stuffed round.
A stuffed bag can cross it
The same 19 × 24 mailer packed to 4 in deep instead of 3 clears 1,728 cubic inches. Depth is the dimension shippers most often ignore when they estimate a bag's size.
What crossing it changes
Past the line, the carrier bills whichever is bigger: the scale weight or the dimensional figure. A light, bulky bag can end up billed heavier than it actually is.
Source: USPS, DMM 123, Nonpresorted Prices, Postal Explorer, read 2026-08-19. Carriers revise pricing rules without notice; check the live page for anything past a flat, light bag.
Common questions
What sizes do shipping bags come in?
Poly mailers are sold in a handful of common flat sizes, measured seam to seam: 6x9, 9x12, 10x13, 12x15.5, 14.5x19 and 19x24 in are the sizes that show up across most suppliers, though exact seam placement varies by brand by a fraction of an inch.
What is the biggest standard poly mailer size?
19x24 in is the largest size most suppliers stock as a standard item, sized for a folded comforter, a pillow, or several garments bundled together. Bigger than that and sellers generally move to a poly bag sold by the roll or to a box.
When does a shipping bag get billed like a box?
Once it crosses roughly one cubic foot. USPS states that parcels exceeding 1,728 cubic inches are billed on the greater of actual weight or dimensional weight, length times width times height divided by 139, per its own mail manual read 2026-08-19. A flat mailer almost never reaches that; one stuffed round and firm can.
How much does it cost to ship in a large poly mailer?
$11.98 for the example on this page: a queen bed sheet set folded into a 19x24 in mailer at 4 lb, Berkeley Heights, NJ to Detroit, MI, on UPS Ground, captured 2026-08-19. A lighter, smaller mailer runs less; price your own item in the calculator.
Should I size the bag to the item or round up?
Size to the item and go up only enough to seal without strain. Weight, not the bag's printed size, drives most mailer shipments, so an oversized bag mainly adds slack that lets the contents shift and the seams work loose in transit.
