How are internal dimensions calculated? Internal dimensions (length, width and height) are based on the product’s external dimensions plus a margin: add 2–5 mm to both length and width (for ease of handling), and add a buffer to the height based on the product’s thickness; for irregularly shaped products (such as wine bottles and cosmetics), measure the most protruding point.
How do you ensure the product does not rattle? The solution to rattling is the inner insert: grooves and compartments secure the product in place; the rattle test (shaking the box without any sound) is the acceptance criterion.
How do you determine if the product fits? The product must lie flat and stable: the centre of gravity should be at the centre of the box, with cushioning around the edges (inner insert, foam); ‘fitting’ does not mean cramming it in, but rather ‘fitting without being squeezed’.
The most tricky aspect of the relationship between the box and the product is that ‘if the box is too big, the item rattles; if it’s too small, the item gets stuck’: a difference of just a few millimetres in the internal dimensions can completely ruin the unboxing experience. This article clearly explains the methodology for calculating the internal dimensions of packaging boxes.
How do you verify this? By creating a prototype box and testing the actual fit: a three-step process of placing the item inside, removing it, and giving it a shake; any changes to the specifications (such as a change of product) must be re-validated from scratch. For small-batch production, produce a prototype before placing an order.
Determining the internal dimensions of a packaging box is a precision task where ‘a difference of a few millimetres makes a world of difference’: fitting the product inside is the bare minimum; being able to remove it easily is a mark of professionalism; and ensuring it doesn’t rattle is a sign of quality — achieving all three makes the unboxing experience a real bonus.
How do we determine ‘easy to remove’? Allowance for removal: enough space for a finger (leave a gap at the edge), the inner tray must be liftable (with a handle hole and finger grip); deep boxes (with high inner trays) require sufficient space for retrieval.
