How this calculator works
A box may have enough cubic capacity while still being too short along one axis to accommodate the product plus protective padding. This tool checks dimensions axis by axis instead of relying on volume alone. It also estimates geometric air space that could require cushioning or bracing.
What the calculation does
Add twice the requested padding thickness to each product dimension to find the minimum internal carton dimensions. Compare those dimensions to the actual carton interior and calculate unused volume as carton volume minus product volume. Use the clearance values to identify the most constrained axis.
Important limitations
Use inside box dimensions and one rectangular item in a fixed orientation. A positive void volume does not ensure practical fit; this calculator does not optimize rotated orientations, shape irregularities, loose-fill expansion, fragile-product protection or carton strength.
Common questions
Should I use outside or inside box dimensions?
Use internal dimensions. Wall thickness reduces actual padding clearance.
Is all empty box volume available for filler?
No. Geometric void is an upper bound only. Material compression, air gaps and protective inserts alter usable fill volume.
Can I rotate the product?
The current comparison uses the orientation entered. Try rearranging the product dimensions to test another orientation.