Internal size and external size answer different questions
Internal dimensions describe the space inside the erected box. They help establish whether the product, inserts and any protective material will fit. External dimensions describe the finished outside size, which matters for storage, pallet layout, conveyors and carrier limits.
For a conventional rectangular case, length is the longer opening dimension, width is the shorter opening dimension, and height runs from the base to the opening. If the structure or opening is unusual, use an annotated drawing rather than relying on those words alone.
Measure the product in its packed arrangement
- Arrange the actual contents as they will be packed, including individual product packaging.
- Record the overall dimensions, total weight and the number of products in each case.
- Include dividers, pads and other protective components in the brief.
- Identify fragile, protruding or compressible parts that may affect the design.
- Share a sample where possible, especially for an irregular shape or a close fit.
Agree the allowance; do not add a fixed amount to every box
The space needed around a product depends on its shape, packing method, protection and the variation in the products themselves. Too little room can make packing difficult; unnecessary space may allow movement or increase material use.
Board thickness and the construction of folds and joints also affect the relationship between internal and external dimensions. Do not convert between them by adding a universal figure. Ask the design team to confirm the finished dimensions on the drawing.
Use a sample to check the whole packing task
Erect the proposed pack using the intended method, load the contents and close it. Check product fit, removal, closure, labels and any inserts. For an automated line, confirm the pack with the equipment and operating conditions it will actually meet.
Record the approved drawing and revision alongside the dimensions. A size such as 300 × 200 × 150 mm is an illustration of the notation, not a recommendation for a particular product or load.
