Shipping Box Size Chart: Common Corrugated Dimensions and What Fits

Q: Are box sizes measured inside or outside?

Corrugated box sizes are quoted as inside dimensions, the usable interior, measured length x width x height. Outside dimensions run slightly larger because of the board thickness.

Packaging Reference

Shipping Box Size Chart: Common Corrugated Dimensions and What Fits

A quick-reference guide to the most-used corrugated box sizes, from small cubes to moving cartons, with typical contents and edge-crush (ECT) notes. Dimensions are listed as length x width x height in inches.

Box sizes are always written L x W x H, measured as inside dimensions so your product actually fits.

Common corrugated box sizes and what fits

Grouped by shape and job. Use the smallest box that holds the item plus light cushioning, dimensions are inside measurements.

Corrugated box quick-reference. Inside dimensions in inches (L x W x H).
Size (L x W x H)	Common name	Typical contents
Small cubes and singles
6 x 6 x 6	Small cube	Mugs, candles, small parts, jewelry boxes, cosmetics
8 x 8 x 8	Standard cube	Glassware, collectibles, mid-size fragile items with padding
10 x 10 x 10	Cube	Shoes, small appliances, bundled apparel, gift sets
12 x 12 x 12	Large cube	Bulk office supplies, small electronics, bundled goods
Flat and rectangular
12 x 9 x 4	Flat mailer box	Books, folded apparel, subscription kits, documents
12 x 9 x 6	Half-cube rectangle	Apparel, boxed retail products, subscription boxes
14 x 10 x 6	Flat rectangle	Framed prints, flat electronics, folded textiles
12 x 8 x 6	Small rectangle	Multi-item orders, kits, hardware, canned goods
Medium
14 x 14 x 14	Medium cube	Kitchenware, medium electronics, multi-pack orders
16 x 12 x 12	Medium rectangle	Small appliances, boxed sets, mid-weight bundles
16 x 16 x 16	X-large cube	Bulk retail, lampshades, lightweight bulky goods
18 x 18 x 18	Jumbo cube	Bulky low-weight goods, bedding sets, bundled soft goods
Moving and storage cartons
18 x 18 x 24	Medium moving box	General household moving, books in split loads, kitchen items
20 x 20 x 20	Large moving box	Linens, pillows, lampshades, bulky lightweight items
24 x 18 x 24	Large moving carton	Bulky low-density items, mixed household goods

A note on ECT (Edge Crush Test): ECT rates how much stacking pressure a box wall can take before it crushes. Most single-wall shipping boxes are commonly rated around 32 ECT, which suits everyday parcels up to roughly 65 lb of contents. Heavier or more fragile loads step up to 44 ECT single-wall or double-wall board. Match the rating to the weight, not just the size, a big light box does not need a heavy wall.

How to use this chart

Measure your product at its longest, widest, and tallest points, then add about half an inch to an inch on each side for cushioning. Find the smallest box on the chart that clears those numbers. A snug fit protects the product and lowers dimensional-weight shipping costs, since carriers bill on box volume as well as actual weight. When an item is dense or fragile, step up the ECT rating rather than the box size.

Shop boxes by exact size

Each size below has its own page with every in-stock construction (ECT grade, kraft or white, pack count) and live case pricing.

Cubes

6 x 6 x 6 · 8 x 8 x 8 · 9 x 9 x 9 · 10 x 10 x 10 · 12 x 12 x 12 · 14 x 14 x 14 · 16 x 16 x 16 · 18 x 18 x 18 · 20 x 20 x 20 · 24 x 24 x 24 · 12 x 12 x 18 · 12 x 12 x 24 · 18 x 18 x 24 · 6 x 6 x 36 · 25 x 25 x 25

Shallow, flat & rectangular

10 x 10 x 2 · 15 x 12 x 4 · 16 x 10 x 4 · 16 x 16 x 5 · 24 x 12 x 6 · 28 x 24 x 6 · 16 x 12 x 6 · 10 x 8 x 6 · 16 x 10 x 6 · 24 x 18 x 12 · 15 x 15 x 10 · 16 x 16 x 14 · 12 x 9 x 10 · 7 x 6 x 5 · 7 x 7 x 4 · 10 x 5 x 5 · 4 x 4 x 6 · 18 x 9 x 9 · 24 x 10 x 8

Long & tall

10 x 10 x 48 · 36 x 12 x 12 · 40 x 12 x 12 · 40 x 20 x 20 · 30 x 30 x 12 · 12 x 12 x 18 · 12 x 12 x 24 · 18 x 18 x 24 · 6 x 6 x 36

Corrugated mailers & tubes

8 x 7 x 4 mailers · 8 x 7 x 3 mailers · 13.5 x 3.5 x 3.5 mailers · 17.5 x 3.5 x 3.5 mailers · 5 x 60 tubes

Need the complete catalog view? The full directory of sizes by dimension lists every stocked footprint.

USPS Priority Mail flat rate box sizes

Flat rate boxes are a fixed-size, fixed-price system — these are the official USPS outside dimensions:

Flat rate box	Outside dimensions
Small Flat Rate Box	8 11/16" x 5 7/16" x 1 3/4"
Medium Flat Rate Box 1 (top-loading)	11 1/4" x 8 3/4" x 6"
Medium Flat Rate Box 2 (side-loading)	14" x 12" x 3 1/2"
Large Flat Rate Box	12 1/4" x 12 1/4" x 6"
Large Board Game Box	24 1/16" x 11 7/8" x 3 1/8"

Inside dimensions run slightly smaller, and flat rate only wins for dense items headed far. The full breakdown — inside dimensions, when flat rate beats your own box, and the crossover math — is in the USPS flat rate box size guide.

Box strength: ECT grades at a glance

Size picks the fit; ECT grade picks the survival. ECT-32 single-wall covers everyday parcels to roughly 65 lb. ECT-44 and ECT-48 double-wall carry dense, stacked, or fragile loads. Compare the ECT-32 size chart, the ECT-44 size chart, or the ECT vs 200 lb burst test guide if your spec sheet uses the older rating.

Frequently asked questions

What sizes are USPS Priority Mail flat rate boxes?

USPS flat rate uses five fixed boxes: small (8 11/16 x 5 7/16 x 1 3/4 in), two mediums (11 1/4 x 8 3/4 x 6 in top-loading; 14 x 12 x 3 1/2 in side-loading), large (12 1/4 x 12 1/4 x 6 in), and the large board game box (24 1/16 x 11 7/8 x 3 1/8 in), all outside dimensions. Postage is fixed per box regardless of weight up to 70 lb.

Are box sizes measured inside or outside?

Corrugated box sizes are quoted as inside dimensions (the usable interior), measured length x width x height. This is what determines whether your product fits. Outside dimensions run slightly larger because of the board thickness.

What is the most common shipping box size?

There is no single answer, but 12 x 9 x 6, 12 x 12 x 12, and 8 x 8 x 8 are among the most widely used for e-commerce because they cover apparel, general merchandise, and small fragile goods respectively.

What does L x W x H mean on a box?

Length is the longer side of the opening, width is the shorter side of the opening, and height is the depth from the opening to the base. Boxes are almost always listed in that order.

How much extra space should I leave around a product?

Roughly half an inch to an inch of clearance on each side is typical, enough room for cushioning without leaving dead space that invites crushing or raises dimensional weight.

Do I need a stronger box for a heavier item?

Yes. Box strength is set by the board's ECT or burst rating, not its size. For heavier or denser contents, choose a higher ECT single-wall board or a double-wall box rather than simply a bigger carton.

Find the right box

Match your dimensions to the collections below.

Shop corrugated boxes Mailer boxes Request a bulk quote

Shipping small, flat, or lightweight items instead? A bubble mailer or poly mailer may cost and weigh less than a box.

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Dimensions and use cases are general industry references for planning purposes; confirm exact interior measurements against the specific box you order.