Allow for the complete contents
Measure every item that will go inside, including caps, sleeves and any inner wrapping. For a gift set, show how you would like the products arranged and whether they should stay in position when the lid opens. An insert needs its own space; it cannot simply be added after the box dimensions have been fixed.
Confirm whether quoted dimensions are internal or external. Board thickness, folds and the wrapped construction affect the outside size. If the finished box must fit a mailer or shelf, tell us that constraint at the start.

