Worked example: orientation changes the count
With a usable box interior of 40 × 30 × 20 cm and identical items of 18 × 10 × 5 cm, one regular orientation gives floor(40/18) × floor(30/10) × floor(20/5) = 2 × 3 × 4 = 24 items. Rotating to 10 × 5 × 18 cm gives 4 × 6 × 1 = 24, while 5 × 18 × 10 cm gives 8 × 1 × 2 = 16. The best regular grid here holds 24.
The volume ratio is 24,000 ÷ 900 = 26.67, but it does not prove that 26 items fit. Each axis needs whole items. A mixed-orientation packing arrangement may differ from the regular grids this tool checks.
Use usable space and protected item dimensions
For fit, use internal box dimensions after liners or dividers, and include the protective envelope around each item. Use external dimensions separately for carrier weight calculations. Test the proposed pack physically: the model does not assess closure, fragility, carton strength, or whether the product may be rotated.
What this fit model checks
The tool checks orthogonal rows and layers. It is useful for identical rectangular products where compression and nesting are not part of the packing plan.
What it deliberately excludes
Mixed products, diagonal placement, flexible packaging, dividers and structural constraints need a more advanced packing model or a physical test.