The honest answer is that it depends on what you ship most often, not on what you ship occasionally. Pull your last hundred orders, find the arrangement that covers the majority of them, and size for that. Outliers can go in a second size or a box.
Work from your actual order profile
| What you ship | What sets the size | What usually goes wrong |
|---|---|---|
| One folded garment | The folded footprint plus the tissue and card | Sized to a flat sample, not to a real fold |
| Prints, posters or artwork | The sleeve or backing board, which is larger than the print | Corners crushed because there was no board |
| Document packs | US letter or A4 plus clearance | Too tight to load quickly at volume |
| Mixed multi item orders | The thickest combination you regularly ship | One size forced to cover every order |
Three questions that settle it
How thick does a typical order get?
Thickness is the dimension that decides both the board and the parcel rate band. Pack a real order, measure it, and then pack the biggest order you would call typical and measure that too. If the two numbers are far apart, you need two sizes.
Does the pack need to arrive flat, or just intact?
Documents and garments only need to arrive intact, so a folding carton or a light E flute mailer is enough. Anything that must not bend, such as prints or framed items, needs a rigid mailer or a stiffener, and that stiffener has to be measured into the internal dimensions.
Is anyone opening it in front of a camera?
If the pack is part of the brand experience, a slightly snug fit with tissue presents better than a loose one. If it is purely functional, prioritise loading speed and let it be a little roomy.
The mistakes that cost the most
- Sizing to the product instead of to the product plus its wrap.
- Buying one size big enough for every order, then paying dimensional weight on every small order for the life of the SKU.
- Quoting an external dimension and receiving a box with less usable space than expected. Always confirm whether the number on your quote is internal or external.
- Ignoring the carrier. Rate thresholds are set by the carrier, so check a filled pack against your own rate card before you commit to a size.
What it costs to get it right
The minimum is 100 mailers. Pricing starts from about $0.48 per unit at bulk volumes and is confirmed on your written quote. Turnaround is quoted per product across three lanes: rush, which is expedited production plus air freight, standard on air, and cost saver on sea, from about 7 business days in production plus 2 to 5 days for delivery. Because the cutting die and plates are included, a mailer cut to your order profile costs no more to tool than one that nearly fits, which is the whole argument for measuring properly once.
The full measuring method is in how to size a flat mailer. To order, see mailer boxes, or send a filled sample measurement with a quote request.
