Mailer boxes are sized around the product, not around a standard. There is a cluster of dimensions that come up constantly in ecommerce because they suit apparel, cosmetics, candles and subscription boxes, and those are set out below. A mailer is a one piece box with a folding lid, so it ships flat and needs no tape, which is why it has become the default for retail orders that a customer opens themselves.
Common mailer box sizes
Written length by width by height in inches, measured inside the opening. If you are unsure which number is which, see how to measure a box.
| Size (LxWxH) | Band | Suits |
|---|---|---|
| 6 x 4 x 2 | Extra small | Jewelry, lip products, sample sets, cards |
| 8 x 6 x 2 | Small flat | Prints, stationery, flat accessories |
| 8 x 6 x 4 | Small | Single cosmetics sets, small candles, mugs |
| 9 x 6 x 3 | Small to medium | Folded tees, small apparel, beauty bundles |
| 10 x 8 x 4 | Medium | The workhorse ecommerce size, apparel and multi item orders |
| 12 x 9 x 4 | Medium wide | Larger apparel, flat multi item sets |
| 12 x 10 x 5 | Large | Subscription boxes, gift sets, homeware |
| 14 x 10 x 4 | Large flat | Framed prints, larger flat goods |
| 16 x 12 x 6 | Extra large | Bulkier gift sets, multiple products together |
What is a standard mailer box size?
There is no official standard, but if one size deserves the label it is 10 x 8 x 4. It holds a folded garment, a small bundle of products, or a modest gift set, and it fits comfortably in most delivery networks. Treat it as the size to try first if you have no other constraint, then adjust from there.
How to pick the right mailer size
- Start from the product at its largest. Measure it packed the way it will actually ship, including tissue, a card, or a dust bag.
- Leave a little clearance, not a lot. Enough to slide the product in without forcing it. Any more and it slides around in transit.
- Depth is where mistakes happen. People get length and width right and then pick a mailer too shallow for the lid to close flat, or so deep the contents shift.
- Consider the unboxing. A mailer is opened by a customer. A product that sits neatly, rather than buried in filler, is the whole reason to use this format.
- Check it against your postage. A slightly smaller mailer can drop you into a cheaper bracket on every order you send.
Mailer box sizes and shipping cost
Carriers compare a parcel’s actual weight against a figure derived from its dimensions and charge on whichever is higher. Mailers are usually light, so the dimensions are what decide the price. Reducing depth by an inch on a product you ship every day is worth more over a year than most people expect. Carriers publish their current rules on their own sites and those rules change, so check the live figures rather than trusting a number in an article.
When to use a mailer instead of a shipping box
A mailer suits retail orders that a customer opens: apparel, beauty, subscriptions, gifting. It ships flat, needs no tape, and looks considered when it arrives.
A shipping carton suits heavier, bulkier or wholesale goods, and anything going into an outer case. If that sounds more like your order, see shipping box sizes instead.
Mailer box size FAQs
What is the most popular mailer box size?
10 x 8 x 4 covers more ecommerce orders than any other single size, with 8 x 6 x 4 close behind for smaller items.
Are mailer box dimensions internal or external?
Internal. What matters is what fits inside, and the outside is slightly larger by the thickness of the board.
Can I order a mailer box in a size not listed here?
Yes. Custom dimensions are the normal way to order a mailer, and there is no minimum, so you can test a size on a small run first.
Do mailer boxes need tape?
No. A mailer folds into itself and holds closed without tape, though many brands add a branded sticker or tape strip for security and presentation.
Related guides
Compare the formats in types of mailer boxes and the full mailer boxes guide. For board and strength choices see the corrugated boxes guide. When you are ready, see custom mailer boxes with no minimum order.