The Box Files · File 03

How to measure
a box

Wrong-size boxes are the most common (and most avoidable) first-order mistake. Here's how dimensions actually work.

4 min read · Southpoint Packaging

The convention: L × W × D, inside

Box sizes are written as length × width × depth, in that order, and they describe the inside of the box — the space your product actually occupies. Length is the longer side of the opening, width the shorter side, and depth is how far down the box goes.

This trips people up constantly: a "12 × 9 × 4" box is smaller on the outside than you'd measure with a ruler, because the board itself has thickness. When in doubt, always quote internal dimensions — that's what manufacturers assume.

Measuring your product

1. Measure your product at its widest points in all three directions. Include anything that ships with it — lids, pumps, protective wrap.
2. Add clearance: about 1/4 inch (6 mm) per side for a snug fit, more if you're adding inserts, tissue, or void fill.
3. If multiple items ship together, arrange them the way they'll actually pack — flat, stacked, or side by side — and measure the arrangement, not the pile.

Why oversizing costs you three times

An oversized box costs more to make (more board), more to ship (carriers price by dimensional weight, not just actual weight), and more to protect (all that empty space needs void fill or the product rattles). It also lands worse: a small product loose in a big box reads as careless to the customer.

Not sure? Say so

If you can tell us what the product is and its rough measurements, we can work out the box size with you — that's a normal part of quoting, not an extra service. Plenty of first orders start with "it's a candle, about this big" and end with a correctly sized box.