MEASUREMENT GUIDE
How to measure length, width, and depth for a box.
Box dimensions normally follow length × width × depth. Length and width describe the opening; depth is measured perpendicular to it. The numbers are incomplete until the specification also says whether they are internal or external and identifies the board used to make the box.
Choose the opening, then keep one order
Start by identifying the opening through which the product enters. On a conventional carton, length is the longer side of that opening, width is the shorter side, and depth runs from the opening to the opposite panel. Some trade specifications use different conventions, so label the axes instead of relying on position alone.
Write the dimensions in one stated order and keep that order in the quote, drawing, sample, and purchase order. A correct set of three numbers in the wrong order produces the wrong structure just as surely as an incorrect measurement.
Internal and external dimensions are not interchangeable
Internal dimensions describe the usable space for the product. External dimensions describe the finished outside size used for pallet, shelf, and shipping calculations. Board caliper, folds, liners, and construction details create the difference between them.
Do not convert by subtracting one thickness from every axis. Each panel stack is different, and corrugated board compresses at creases. Use the template's own allowance model, then confirm it with the actual material and a physical sample.
A practical measuring checklist
Measure the product at its widest stable points, include inserts or protective parts, and add only the clearance the packing process needs. Record units beside every value. For an existing box, square it before measuring and take internal dimensions with the flaps out of the way.
Before tooling, test the result with a representative product and the production board. Check fit, closure sequence, compression, and the space needed by operators or packing equipment.
Try the measurement order on live templates
Each template exposes the dimensions it accepts and rebuilds the dieline from those values.