Wrong dimensions are the most common cause of packaging rework. A box that is 5 mm off can mean a product that rattles, a die that must be recut and a deadline that slips. Measuring correctly takes five minutes.
The convention: Length x Width x Height
Dimensions are written L x W x H. Length is the longer of the two opening dimensions, width is the shorter, and height is the depth. For a box that opens on top: measure the opening first, then the depth.
Inner vs. outer dimensions
Packaging factories quote inner dimensions ??the usable space inside the box. If you measure the outside of an existing box, you are measuring outer dimensions, which include wall thickness. Always state which you mean. For corrugated shipping boxes, outer dimensions also determine freight cost, so both matter.
Measure the product, not the box
For a new box, measure the product at its widest, deepest and tallest points, including any protrusions, caps or hang-tabs. Add allowance for a snug but not tight fit ??and remember the product must clear the top opening during insertion.
Common mistakes
- Ordering W x H instead of L x W x H and getting a sideways box.
- Forgetting insert thickness (trays, dividers) when sizing the outer.
- Ignoring that corrugated boxes bulge slightly when filled.
- Mixing units ??mm, cm and inches in one quote.
Send your dimensions in millimetres, state inner or outer, and include a photo of the product. That alone will make your quote request dramatically smoother.