Packaging Reference Library · Wall Charts

Box Measuring Diagram

The Length x Width x Depth convention for corrugated boxes, measured as inside dimensions from the opening, and how to avoid common ordering errors.

Ref PK-0205ASTM D5118

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

The box industry states box size as Length x Width x Depth (L x W x D). The numbers are always inside dimensions, and always in that order. Length and width describe the opening. Depth is the distance from the opening to the other end. The order matters: a 12 x 10 x 6 box and a 6 x 10 x 12 box hold the same volume but open on different faces.

How to measure

Stand the box so you look into the opening, the end closed by the flaps.
Length (L): the longer side of the opening.
Width (W): the shorter side of the opening.
Depth (D): from the opening to the opposite end. Depth can be larger than length.
Measure inside, from inner wall to inner wall, with the box squared up.
Write the size as L x W x D.

Measurement reference

Dimension	Where it is measured	Tip
Length	Longer side of the opening	Always the first number
Width	Shorter side of the opening	Always the second number
Depth	Opening to the opposite end	Sometimes called height
Inside dimension	Wall to wall, inside	What the product needs
Outside dimension	Over the outer surfaces	What carriers and pallets see
Board allowance	Difference between inside and outside	Depends on flute; check the maker's allowance

Key points

Inside dimensions are what you order. Outside dimensions are what you use for pallet patterns, shelf space and carrier dimensional weight.
Outside dimensions are larger than inside dimensions by roughly the board thickness on each side, plus allowances that vary by maker and flute.
For a top-loading box (opening on top), depth is the height. For an end-loading box (opening on the end), depth is the long dimension.
Allow room for the product plus any cushioning or dividers when you size a box.
Folding cartons and die-cut mailers may be quoted differently. Confirm the maker's convention.

Common mistakes

Listing the numbers in the wrong order and getting a box that opens on the wrong face.
Measuring outside dimensions and ordering them as inside dimensions, so the product does not fit.
Calling the tallest dimension "length" on a top-loading box.
Forgetting cushioning space and buying a box that fits the bare product only.
Measuring a box that is not squared up.

Governing standards: ASTM D5118 (fabrication of fiberboard shipping boxes); the box maker's dimensional conventions.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

More in Wall Charts

← All Packaging sheets