Mailer Box Sizes: A Simple Size Chart for Online Stores

Why the size matters more than the print

Most brands spend weeks on the artwork and five minutes on the size. It should be closer to the other way round. The size decides how much board you pay for, how much void fill you need, whether the product rattles in transit and, most of all, what the courier charges you.

A box that is just 2 cm too big in each direction can push a parcel into a higher shipping band. You pay that difference on every order, for as long as you use the box. Getting the size right once is one of the easiest savings an online store can make.

Mailer box size chart

These inside sizes cover most of the orders we see. They are a starting point, not a rule: a custom size costs the same to make as a standard one, so always size the box to your product.

How to measure your product the right way

Measure the product the way it will sit in the box: wrapped in its tissue, inside its pouch or sitting in its insert. Then write the size in this order:

Length: the longer side of the opening when the lid is up.

Width: the shorter side of the opening.

Height (depth): from the floor of the box to the underside of the closed lid.

Add about 5 to 10 mm (roughly 1/4 inch) to each measurement so the product slides in without forcing it and without rattling. Soft items such as clothing need less room; rigid items such as jars need a little more, or an insert.

Always send the inside size and say so. The outside of a mailer is a few millimetres bigger because of the board thickness, and mixing the two up is the most common sizing mistake.

Box size and your shipping bill

UPS, FedEx and many other couriers charge for whichever is greater: the real weight or the dimensional weight. Dimensional weight is worked out from the box size. For US shipments in inches and pounds, the common formula is length x width x height divided by 139.

Here is what that means for a light product such as a T-shirt that weighs under 1 lb:

Pick a size by product type

If you are not sure where to start, these are the sizes we most often recommend for each kind of store.

Clothing: 10 x 8 x 4 for a single tee, 12 x 9 x 4 for hoodies or two items. Fold the garment the same way every time so the box always fits.

Cosmetics and skincare: 6 x 4 x 2 for one product, 8 x 6 x 3 or 9 x 6 x 3 for a set, with an insert so bottles do not move.

Candles: 8 x 6 x 3 for a single jar candle, with a corrugated insert. Glass needs to be held, not just packed in.

Subscription boxes: 10 x 8 x 4 is the most popular size because it fits a mix of items and still looks generous when opened.

How many sizes should you order?

One box for everything sounds simple, but it usually means most orders ship in a box that is too big. Ten sizes is the opposite problem: small runs of each, higher prices per box and a packing table full of stock.

For most stores, two or three sizes is the sweet spot. Sort your last few hundred orders by what was inside, find the two or three most common groupings, and size a box for each. Use the same artwork on all of them so they still look like one brand.

Get the size checked before you order

Send us your product size and weight, or just a photo of it next to a ruler, and how you ship. We will suggest the inside size and board, and reply with a price and a free dieline, usually within an hour during business hours.

Custom mailer boxes start from 100 pieces, so you can test a size with real orders before committing to a bigger run. Production takes about 12 to 15 business days after you approve the proof.