Packaging buying guide
How to Measure a Box for Custom Packaging
Use internal dimensions to check whether the product fits, and external packed dimensions for transport. Always label which measurement you are supplying, use one unit and check the arrangement with a physical sample.
Four measurements that should not be mixed
| Measurement | What it describes | Used for |
|---|---|---|
| Product size | The item as it will be packed, including its existing retail pack if applicable. | Starting the structure and layout. |
| Usable internal box size | The available space inside the assembled box, after accounting for its construction. | Checking product, insert and wrapping fit. |
| External box size | The outside of the closed, assembled box. | Fitting a bag, outer mailer or storage space. |
| Shipping carton size | The outside of the carton containing multiple boxes or complete sets. | Planning bulk freight and warehouse space. |
A single number labelled “box size” is not enough when several of these measurements are in use. Include a photograph or sketch showing the measurement direction.
Measure the complete packed arrangement
- Arrange the products exactly as the customer should receive them.
- Include the retail container, insert, tissue, cards and protection.
- Measure length, width and height in one unit, preferably millimetres.
- Mark which side opens and whether the measurements are product or internal box dimensions.
- Share any fit constraints, such as a paper bag, shelf or outer mailer.
There is no universal extra allowance suitable for every product. Soft garments, rigid bottles, inserts and wrapping require different fit reviews. Ask the supplier to propose the clearance and then check it with the actual item.
Check the structure-specific details
For a drawer box, measure the usable inner tray and review how the insert affects removal. The outside sleeve is not the packing space. Check that the drawer can move with all components inside.
For a corrugated mailer, review the inside of the fully folded box. Tuck tabs, doubled edges and protective inserts may affect the usable area. Check that the lid closes without pressing on the product.
For a magnetic gift box, review the usable base and lid clearance, including the highest point of the filled gift set. The outside height alone does not establish the available internal height.
Use a worked example without treating it as a specification
Suppose a folded garment measures 300 × 220 × 40 mm before wrapping. These are product measurements, not an approved box size. Adding tissue and a card, changing the fold, or packing a second garment changes the arrangement.
Send the measured product, its packing reference and the number of garments per box. Ask for proposed internal dimensions and a plain sample. After fit approval, confirm the corresponding external box and shipping carton dimensions. This avoids ordering a box based on an assumed allowance.
Confirm dimensions and tolerances before artwork
The approved dieline should show the structure and artwork panels. Record the finished size, whether it is internal or external, and any agreed manufacturing tolerance in the written specification. Do not assume dimensions on an unapproved reference drawing are final.
A digital proof helps check text, logo placement and artwork orientation. A physical structural sample checks fit and opening. Keep both approvals with the order so a later artwork revision does not accidentally change the agreed structure.
What to send with your quotation request
Include product measurements, photographs, quantity per size, the preferred box type, wrapping and insert requirements, destination country or postcode and the delivery target. If the dimensions are undecided, say so and provide a packing reference instead of inventing a finished size.
For freight, request carton quantity, external carton dimensions and gross weight once the packing method is known. The dimensions of one presentation box cannot be substituted for the carton data used to transport a bulk order.