Standard Box Sizes: The Complete Chart for Shipping, Mailer and Product Boxes

Is there such a thing as a standard box size?

Search for "standard box sizes" and you will find dozens of charts that do not quite agree with each other. That is because there is no official US standard for box dimensions. What exists instead is a set of sizes that box makers, distributors and carriers have converged on over decades, because they fit common products, stack well on a 48 × 40 in pallet and come off existing dies and corrugator settings efficiently.

So when this guide says "standard", read it as common stock size: a size you can usually buy off the shelf from several suppliers, in plain brown corrugated, within a few days. Custom boxes, by contrast, are made to whatever length, width and height your product needs, and can be printed.

The charts below collect the sizes that come up again and again across stock catalogs, carrier programs and our own quoting. Use them to:

• get a quick sense of what size range your product falls into,
• compare a stock box against a right-sized custom box,
• plan inserts, cases and pallets around sizes that already work,
• and avoid ordering a box that looks fine on paper but wastes space in transit.

How box sizes are written

Every chart on this page uses the packaging industry convention:

Length × Width × Height (L × W × H), inside dimensions, in inches.

• Length is the longer side of the opening.
• Width is the shorter side of the opening.
• Height (also called depth) runs from the opening to the bottom.

The opening matters. A 12 × 9 × 4 in mailer opens on its 12 × 9 face and is 4 in deep. A 4 × 9 × 12 box would be a tall carton opening on a small end. If you are unsure which side is which, our step-by-step guide on how to measure a box walks through every common style.

Two more conventions are worth knowing:

1. Inside vs outside. Box makers quote inside dimensions so your product fits. Carriers measure the outside, which is larger by roughly the board thickness on each side: about 1/8 in overall for E-flute, 1/4 in for C-flute and 1/2 in for double-wall.
2. Whole inches. UPS, FedEx and, under its 2026 rules for larger parcels, USPS round each outside dimension up to the next whole inch when they calculate dimensional weight. A 12.1 in side is billed as 13 in. That is one reason common stock sizes tend to be whole numbers.

Standard shipping box sizes (RSC)

The regular slotted container (RSC) is the classic brown shipping box with four flaps on top and bottom. It is the most economical box per cubic inch of space, which is why distributors stock it in hundreds of sizes. The sizes below are among the most widely stocked.

Small shipping boxes (up to 10 in)

Medium shipping boxes (11–18 in)

Large shipping boxes (over 18 in)

Large boxes are where costs climb fastest. A 24 × 24 × 24 in box with 15 lb of contents has a dimensional weight of about 100 lb at a 139 divisor (13,824 ÷ 139 ≈ 99.5, rounded up), so you pay for far more than the product weighs. If your product is large but light, a custom size or a different format, such as a vacuum-packed bag inside a smaller box, is worth pricing.

Standard mailer box sizes

Mailer boxes (roll-end tuck-front boxes) are the printed, self-locking boxes that most direct-to-consumer brands use. Because they are often custom printed, they are less standardized than RSCs, but a handful of sizes cover most orders.

Mailers are typically made from E-flute or B-flute corrugated. E-flute gives a crisp printed surface and tight folds; B-flute adds crush resistance for heavier contents. See our mailer boxes page for the full specification range.

USPS flat rate box sizes

USPS Priority Mail Flat Rate boxes are free from USPS and charged at one price regardless of weight (up to 70 lb) and, broadly, destination within the US. They are useful benchmarks because so many small businesses start with them. Dimensions below are the inside sizes USPS publishes for its common flat rate boxes; check the USPS site before you rely on them, as programs and sizes are updated from time to time.

Flat rate boxes are economical for heavy, small items. For light items, a right-sized box at commercial weight-based rates is usually cheaper. They also cannot be printed with your brand, and USPS packaging is intended only for USPS shipments.

Standard moving box sizes

Moving boxes are sold by volume class rather than an exact size, and dimensions vary by retailer. These are typical:

The rule movers use applies to shipping too: heavy items go in small boxes, light items in large ones. A large box full of books is hard to lift and likely to fail at the bottom seam.

Standard product box and carton sizes

Retail folding cartons are almost always custom-sized, because they are built around a specific bottle, jar or tube. Still, some sizes recur because the containers inside them are standardized. These are indicative ranges based on common containers; always measure your own.

For anything regulated, such as supplements, cosmetics and food, the carton must also hold all required label text at a legible size. That sometimes forces a carton a little larger than the container alone would need. Our labeling and compliance guide covers the panel rules.

Popular box sizes by product type

If you are starting from a product rather than a box, these pairings are common starting points. Each assumes a product wrapped in tissue or held by a simple insert; fragile items need more room for cushioning.

Our box size finder does this matching for you: enter product dimensions and packing style and it recommends a box size and style, with clearance built in.

Envelope and flat mailer sizes for comparison

Some products do not need a box at all. Soft goods, prints and documents often ship cheaper in a padded mailer or a rigid flat mailer. For reference:

If you are weighing a poly mailer against a box for apparel, our poly mailers page compares protection, cost and recyclability honestly.

Stock box or custom size?

Stock boxes are fast and cheap per unit at low volumes. Custom boxes cost more per unit at very small quantities but pay back in three ways:

1. Shipping. A box that matches your product removes empty space, and carriers charge for space. Cutting one inch from each side of a 14 × 10 × 8 in box takes it from 1,120 in³ to 819 in³, about 27% less volume, and drops billable weight from 9 lb to 6 lb at a 139 divisor.
2. Damage. Products that cannot move inside the box break far less often. Less void fill also means less packing time.
3. Brand. A printed box, inside or out, turns a delivery into a moment customers remember.

A simple way to decide:

• Under about 100 orders a month, or many different product sizes: stock boxes plus a printed sticker, stamp and card usually make sense.
• A few hundred orders a month in a handful of product sizes: price a custom mailer in one or two sizes. Compare the box cost difference with your shipping saving.
• Over a thousand orders a month: custom sizes almost always win. Consider a family of two to four sizes that covers most orders.

How to build your own size range

Brands that ship many products rarely need a unique box for each one. The goal is a small family of sizes that covers most orders with little empty space. Here is a simple process that works for most catalogs:

1. Export three months of orders with the items in each order.
2. Group orders by the packed size they need (measure the products with their wraps and inserts).
3. Find the clusters. Usually 60–80% of orders fall into two or three size groups.
4. Design one box per cluster, sized to the largest typical order in that group plus clearance.
5. Handle outliers with a stock RSC rather than adding another custom size.
6. Review every six months, because product mixes change.

A candle brand might end up with a 5 × 5 × 5 in mailer for one candle, a 10 × 5 × 5 in mailer for two, and a stock RSC for bundles. An apparel brand might use 10 × 8 × 2, 12 × 9 × 4 and 14 × 10 × 4 in. Our box sizing and DIM weight guide has a worked example with real numbers.

Carrier size and weight limits to keep in mind

Even a perfect box is useless if a carrier will not take it at a normal rate. Limits change, so treat these as typical figures and confirm with each carrier's current service guide:

Length + girth = the longest side plus twice the sum of the other two sides. A 24 × 18 × 18 in box has a girth of 2 × (18 + 18) = 72 in, so length + girth = 96 in.

Surcharges often begin well before the hard limits, for example when the longest side exceeds about 48 in or the second-longest exceeds about 30 in. If your box is close to any threshold, shaving a few inches can remove a surcharge that costs more than the box.

Board strength for common box sizes

Size and strength go together. Larger boxes carry heavier loads and stack under more weight, so they need stronger board. A rough guide for single-shipment parcels:

The Edge Crush Test (ECT) measures how much force the board can take on its edge, which predicts stacking strength. If your boxes will be stacked in a warehouse or on a pallet, check the numbers with our box strength calculator and read the packaging materials guide for flute and grade details.

Pallet-friendly box sizes

If you ship wholesale or to fulfillment centers, the 48 × 40 in GMA pallet is the US standard. Boxes whose footprints divide evenly into 48 × 40 in stack with no overhang and little wasted space. Examples:

Overhang is a real problem: a box that hangs over the edge of a pallet loses much of its stacking strength at that corner. Our pallet calculator shows layers, boxes per pallet and overhang for any case size.

Common mistakes when choosing box sizes

• Using the product's size as the box size. Products need clearance for wraps, inserts and tolerances. A box that "fits exactly" on paper is often too tight in reality.
• Mixing up inside and outside sizes. Ordering a custom box by outside size can leave it too small; rating shipping costs by inside size understates them.
• Writing dimensions in the wrong order. 9 × 6 × 3 and 3 × 6 × 9 describe very different boxes.
• Ignoring dimensional weight. A box an inch too big on each side can cost a third more to ship.
• Choosing too many sizes. Every extra size adds inventory, storage and packing decisions. Two to four sizes cover most catalogs.
• Forgetting the pallet. Wholesale cartons that do not fit a 48 × 40 in pallet waste freight space on every shipment.

How to order a custom size

When you are ready to move beyond stock sizes, send a supplier:

1. The product's dimensions (or a sample), including caps, handles and any packaging inside.
2. What goes in the box with it: inserts, tissue, cards, accessories.
3. The style you want (mailer, RSC, tuck end, rigid) or the job the box must do.
4. Quantity and how often you will reorder.
5. Print: outside only, inside and out, or plain.

We turn that into a dieline and a 3D proof, with the inside dimensions shown. Nothing is produced until you approve. You can start with the quote form or build the box yourself in the box builder.

Summary: standard box sizes at a glance

• There is no single official chart. "Standard" means widely stocked.
• Write and read sizes as L × W × H, inside, in inches.
• Popular shipping boxes: 6 × 6 × 6, 8 × 8 × 8, 10 × 8 × 6, 12 × 12 × 12, 16 × 12 × 8, 18 × 18 × 18 and 24 × 18 × 18 in.
• Popular mailers: 6 × 4 × 2, 8 × 6 × 2, 9 × 6 × 3, 10 × 8 × 4 and 12 × 9 × 4 in.
• Check dimensional weight and carrier limits before you commit to a size.
• Once you ship a few hundred orders a month, a small family of custom sizes usually saves money.

GuideHow to measure a box (L × W × H)Which side is length, width and height, inside vs outside dimensions, how to measure mailers, tuck boxes and rigid boxes, and how to order a size that fits. GuideBox sizing & DIM weightHow to measure inside vs outside box size, choose clearances, calculate UPS, FedEx and USPS dimensional weight, and right-size boxes to cut shipping costs. GuideMailer box vs shipping boxMailer boxes and shipping boxes (RSCs) compared on structure, strength, print, packing speed, cost per unit and customer experience, with real price examples. Box StylesShipping BoxesPrinted corrugated regular slotted cartons (RSC) for e-commerce, wholesale and freight.

Sources and further reading

Official and standards-body pages we used for this guide. Rules and standards are updated from time to time, so check the current version before you rely on them.

• USPS Flat Rate quick reference: current Flat Rate box and envelope options.
• UPS packaging guidelines (PDF): carrier guidance on boxes, cushioning and sealing.

Related products & pages

Box StylesShipping BoxesPrinted corrugated regular slotted cartons (RSC) for e-commerce, wholesale and freight. Box StylesMailer BoxesSelf-locking corrugated mailers printed inside and out. The go-to box for DTC brands and subscriptions. Free toolBox Size FinderFind the right inside and outside box size for your product. Free toolDIM Weight CalculatorBillable weight for UPS, FedEx and USPS, and how to cut it.