Inside to outside dimensions calculator
Turn a box's inside dimensions into its outside size, based on the board it's made from.
How it works
Box makers quote inside dimensions. Carriers measure the outside. The difference is the board: each wall adds one thickness to the length and width, and a regular slotted container adds about four thicknesses to the height because the flaps overlap at top and bottom.
It looks small, but carriers round every side up to the next whole inch, so a quarter inch of board can add a full pound of dimensional weight. Read more in inside vs outside box dimensions.
Results are estimates based on typical industry values. Confirm final specifications with your supplier or carrier.
Frequently asked questions
How much bigger is the outside of a box?
For standard C-flute board, about 5/16 inch on length and width and about 5/8 inch on height. Double wall adds roughly twice that.
Which dimensions go on a shipping label?
Outside dimensions. Carriers measure the outside of the package, including any bulge.
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