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Packmetry

Single-item box sizing

Find the internal box size one item actually needs.

Enter one rectangular item, choose how it may rotate, and see the distinct minimum internal box profiles that can contain it. If you already have a box, you can check that box's internal dimensions too.

Calculator

Size a box for one rectangular item

Enter one item's dimensions and its allowed rotation policy. Packmetry will show the distinct minimum internal box profiles that can contain that item geometrically.

Item dimensions
Rotation policy

Rotation changes which item axis can map to each internal box axis. The tool follows the same four rotation-policy labels used by Packmetry.

Optional box check

Already have a box? Enter its internal dimensions in the same unit. Leave all three fields blank if you only want minimum profiles.

What “minimum” means

A geometric minimum, not a packaging allowance recommendation.

Each result profile matches one allowed orientation of the item. The box needs at least those internal dimensions for that orientation. Packmetry does not add a hidden padding, void-fill or manufacturing-tolerance allowance.

Rotation matters

The same item can require different axis dimensions.

With unrestricted rotation, an item can map its original length, width and height to different box axes. Upright and vertical-axis-only policies keep the original height on the vertical axis; fixed orientation keeps all three axes as entered.

Worked example

120 × 80 × 40 mm, kept upright.

The distinct minimum internal profiles are 120 × 80 × 40 mm and 80 × 120 × 40 mm. The height remains 40 mm because the item stays upright.

Single item only

Multiple items need a packing plan.

This calculator does not arrange several items, choose among multiple cartons or calculate protective spacing. For a real multi-item problem, open the Personal workspace or use the Business workspace for inventory, cost and weight inputs.

Internal vs external dimensions

Packing fit uses the inside of the box.

This tool compares the item against internal box dimensions because those describe usable packing space. External dimensions serve a different purpose, including dimensional-weight analysis. Use the dimensional-weight calculator when you need that shipping-volume calculation.