Easy Box Packaging

Size Guides

Mailer Box Sizes: Standard Dimensions for Ecommerce

A medium mailer box is typically 9" × 6" × 3". Size chart for small, medium, and large mailer boxes, plus subscription box and branded ecommerce footprints.

Published
Written by
Maria A · Director
Mailer Box Sizes
Jump to section6 sections
  1. Mailer Box Size Chart
  2. Mailer Box vs. Shipping Carton: Which One Do You Need
  3. How to Measure for a Mailer Box
  4. The Self-Locking Trade-off
  5. Custom Mailer Box Sizes
  6. The Bottom Line

A standard mailer box for e-commerce runs about 12 × 9 × 4 inches. That size fits apparel and small multi-item orders. Mailer boxes are a different animal from the corrugated shipping cartons in our shipping box sizes guide. They’re flatter, self-locking, and built to double as part of the unboxing experience. The chart below covers the full size range, plus when a mailer box is the wrong choice entirely. This post is part of our size guide series, alongside our cake box sizes guide. For everything else, our full box size guide covers the rest.

Mailer Box Size Chart

Size Category

Dimensions (L×W×H, inches)

Dimensions (cm)

Typical Use

XS

6 × 4 × 2 in

15.2 × 10.2 × 5.1 cm

Jewelry, small accessories

Small

9 × 6 × 2 in

22.9 × 15.2 × 5.1 cm

Snack and beauty subscriptions

Small-Medium

10 × 7 × 2 in

25.4 × 17.8 × 5.1 cm

Beauty boxes, small retail sets

Medium

12 × 9 × 3 in

30.5 × 22.9 × 7.6 cm

Apparel and lifestyle subscriptions

Medium-Large

12 × 9 × 4 in

30.5 × 22.9 × 10.2 cm

Most common ecommerce mailer size

Large

16 × 12 × 4 in

40.6 × 30.5 × 10.2 cm

Bulkier apparel, multi-item orders

Every size above tops out at 4 inches of height. That’s the format’s defining trait. Mailer boxes stay flat and wide rather than tall. That’s exactly what makes them different from the shipping cartons in our other guide.

Mailer Box vs. Shipping Carton: Which One Do You Need

A mailer box is a single sheet of corrugated board. It folds into shape and locks with tabs, no tape required. A shipping carton works differently. It’s built from separate panels taped shut, and it can go much taller and hold much more weight.

That construction difference decides which one fits the job. Mailer boxes work well for flat or semi-flat products: apparel, books, subscription sets, small retail goods. They’re not built for anything heavy, fragile, or tall enough to need real vertical clearance. For those, the corrugated cartons in our shipping box sizes guide are the better fit. The corrugated flute types guide covers which flute gives that carton the right crush resistance for your product weight and shipping distance. A quick way to decide: would the product sit flat on a table without rolling or toppling? If yes, a mailer box probably works. If it needs to stand upright, or stack multiple layers deep, reach for a carton instead.

How to Measure for a Mailer Box

Lay the product flat. Measure its length and width at the widest point, then add a half inch of clearance on each side. Height works differently here than it does for a shipping carton. Most mailer boxes stay under 4 inches, so stack whatever’s going inside and measure the actual stacked height. Don’t just measure the tallest single item and assume the rest will fit around it.

Printed mailer boxes add one more variable: interior branding. A folded insert card or a layer of tissue paper adds up to half an inch of extra height. That’s easy to forget when sizing the box off the product alone. It’s the most common reason a “perfectly sized” mailer box arrives looking overstuffed.

The Self-Locking Trade-off

Products that fit this guide

A few Easy Box Packaging products that fit what this article covers.

Illustrative custom-printed subscription mailer box in navy, seafoam, coral, and ivory

Mailer & Shipping Boxes

Subscription Mailer Box

A custom-printed corrugated mailer designed for repeat subscription shipments, consistent inside-lid reveals, insert planning, and efficient recurring fulfillment.

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Closed kraft mailer with forest green VELNORA artwork printed on the lid.

Mailer & Shipping Boxes

Custom Mailer Boxes

Custom mailer boxes coordinate the packed size, closure and printed presentation of an e-commerce order. Discuss corrugated construction, inside and outside artwork, and any insert or divider requirements. Easy Box Packaging reviews the proposed specification and proof before production, with the final board, finish and delivery terms confirmed in your quote.

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Open ivory ecommerce mailer with a folded burgundy knit garment and Norwood Mail Co. print on a studio surface

Mailer Boxes

Custom Ecommerce Mailer Boxes

Custom ecommerce mailer boxes are made-to-order folding boxes sized around the packed length, width, and height of your order. Choose a corrugated or paperboard format, an integrated tuck-in closure, exterior or interior print, and a finish that suits the unboxing experience without adding avoidable bulk around the product.

Request a Quote
Open kraft literature mailer with catalog sheets visible inside

Mailer Boxes

Custom Literature Mailer Boxes

Custom literature mailer boxes built as a flat, auto-lock-bottom corrugated mailer sized around catalogs, brochures, or printed materials. Printed with your own branding inside and out, and sized close to the contents rather than built for a bulkier product.

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Closed kraft retail shipping box with printed panels, tuck closure, and clean scored folds

Retail Packaging

Custom Retail Shipping Boxes

Custom retail shipping boxes are sized around the packed product, the opening sequence, and the route from fulfillment to customer. Corrugated or paperboard construction, printed exterior and interior panels, practical closures, and optional support can be reviewed together so the box works as both a shipper and a retail touchpoint.

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Stack of printed corrugated carton sheets with one sheet lifted beside a carton blank

Corrugated Boxes

Custom Corrugated Carton Sheets

Custom corrugated carton sheets give brands a flat, made-to-order component for dividers, protective layers, carton blanks, printed inserts, and packaging panels. Share the finished sheet format, packed-product arrangement, board direction, quantity, handling route, and artwork status so any scores, cuts, print coverage, and finish can be reviewed together.

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Self-locking tabs are the whole appeal of a mailer box. There’s no tape gun, no dispenser, and a cleaner unboxing moment when the customer opens it. That convenience has a limit, though.

A taped shipping carton seals every edge under real pressure. A self-locking mailer relies on friction and the fold of the board itself instead. It holds up fine in normal handling. It’s not the right choice for anything that needs to survive rough transit. The same goes for anything sitting at the bottom of a stack of heavier packages. Most brands use a mailer box for the final customer-facing package. They wrap a shipping carton around it for anything going any real distance. That’s especially true through a busy fulfillment network with multiple handoffs.

Custom Mailer Box Sizes

The chart above covers standard subscription and retail sizes. It doesn’t cover oddly shaped products or multi-compartment inserts. It also doesn’t cover branding elements like a magnetic flap. A printed interior that needs specific dimensions to look right falls outside the standard chart too.

Easy Box Packaging builds mailer boxes to the exact size and branding a product needs, self-locking tabs included. A box that’s an inch too tall looks half-empty the moment a customer opens it. That undercuts the whole reason to use a printed mailer in the first place. The unboxing moment is often the entire point of choosing this format.

The Bottom Line

Mailer boxes and shipping cartons solve different problems. Picking between them comes down to what’s inside: flat and light favors a mailer, heavy or fragile favors a carton. Get a quote and get a mailer box sized and branded to match what you’re actually shipping.

Questions, answered

Frequently Asked Questions

What’s the most common mailer box size?

12 × 9 × 4 inches. It fits most apparel and small multi-item subscription orders without excess empty space.

Can I ship heavy items in a mailer box?

Not reliably. Mailer boxes are built for flat, lightweight products. Heavier or fragile items are safer in a taped corrugated shipping carton.

Do mailer boxes need extra padding inside?

Usually a little. Even a well-fitted mailer box benefits from tissue paper or a thin insert. It stops light items from sliding during transit, especially on longer shipping routes.

Get the right size

Need mailer boxes sized to your products?

Share your product dimensions, quantity, and how it will be sold or shipped. Easy Box Packaging will review the specification and send a quote, with the minimum confirmed for your exact format.

Mailer Box Sizes Dimensions Chart | Easy Box Packaging