When specifying a box, first decide whether you are sharing the space available inside the box or the overall outside size. These dimensions answer different questions: inside size helps describe product fit; outside size can matter for storage, equipment, loading, or transport limits.
Measure in length × width × height order
- Length: one side of the box opening; suppliers commonly use the longer opening dimension as length.
- Width: the other side across the opening.
- Height: the distance from the inside base to the top opening, with the box erected.
Write the unit beside the measurements, for example 300 × 200 × 150 mm (inside dimensions). Do not send three numbers without saying which dimension convention and unit you mean.
If you already have a box
- Open or erect it so you can identify the inside surfaces.
- Measure the usable space between the inside walls, then the inside height from base to opening.
- Record the numbers in the same length × width × height order.
- If you also have a machine, shelf, pallet, or courier limit, share the maximum outside dimensions separately.
If you are measuring the product
Measure the packed item in the orientation it will sit in the box. Include any parts that protrude or a primary pack that will remain around the product. If you plan to add cushioning, dividers, or other protective packing, mention that too. The supplier can then discuss the required usable space and any allowance needed for the chosen material and design.
A custom box should not be specified by adding an arbitrary clearance amount: the right fit depends on the item, protective materials, and box construction. Ask for confirmation of the final internal dimensions before approving the order.
Copy this note into your enquiry
Box style: [shipping carton / mailer / other]
Dimensions: [L × W × H] [mm / cm / inch]
Measurement type: [inside / outside]
Product and protection: [what goes inside; inserts or cushioning]
Quantity and delivery city: [details]
For additional terminology, the Fibre Box Association’s regular slotted container guideline defines inside dimensions in length, width, and depth order and notes that outside dimensions should be considered for forming, loading, sealing, palletisation, and distribution.
This is a preparation guide, not a manufacturing drawing. Have the box maker confirm dimensions, tolerances, and final fit for your product.