Ordering a custom box comes down to three numbers, and getting them slightly wrong is the easiest mistake in packaging. A box that’s a shade too small won’t close; one that’s too big lets the product slide, invites damage, and looks half-empty on arrival.
The good news is that measuring is genuinely simple once you know which number goes where, and which object to measure first.
The L × W × D convention
Boxes are described as length × width × depth, and the order matters because a printer reads it literally. Picture the box sitting the way it’ll be used, with the opening facing up.
- Length is the longer of the two sides of the opening.
- Width is the shorter side of the opening.
- Depth is how far down the box goes from that opening to the base.
Length and width describe the mouth of the box; depth is the drop. Give the three numbers in that order every time and there’s far less room for a mix-up.
Internal versus external dimensions
This is the difference that catches people out. A box has an outside and an inside, and the gap between them is the board itself.
For a snug product fit, you care about internal dimensions — the space your item actually lands in. For shelf space or shipping-carton planning, external dimensions matter, because that’s the footprint the box takes up. Thicker board widens that gap, so a corrugated box has a more noticeable difference than a thin folding carton.
When you enquire, tell us whether your numbers are the product size or the finished box size. That one line saves a lot of back-and-forth.
Measure the product first
Here’s the order that prevents most errors: measure the thing going in the box before you think about the box at all.
Take the length, width and height of your product at its largest points. Then add a little clearance — enough for tissue, a wrap, or a protective sleeve if you use one, plus a touch of breathing room so it isn’t a wrestling match to pack. That clearance is a judgement call, not a formula; err towards snug rather than roomy.
If your product has an awkward shape, measure the widest and tallest points rather than the average. A handle, a lid, a raised label — the box has to clear the biggest part, even if most of the item is slimmer. Measuring the slim bit and forgetting the bulge is a classic way to end up with a box that almost closes.
The classic mistake: measuring a box you like
It’s tempting to grab a box you already own, measure that, and order the same. Sometimes that works. Often it doesn’t, because you’re copying a size that was designed around a different product.
Measure the item you’re actually selling. The box exists to serve it, not the other way round. A box built around the product almost always uses less material and looks more deliberate than one borrowed from something else.
There’s a related trap worth naming: rounding up “to be safe”. A generous centimetre here and there feels harmless, but it adds up to a loose box, wasted board and a product that shifts in transit. Precision is kinder to the product than padding. If you genuinely need a margin, add it as deliberate clearance rather than vague slack.
Flat products and tall products
Depth is where shapes pull in different directions, so it pays to think about the journey of the product.
Flat products
Cards, prints, jewellery on a pad, thin cosmetics — these want a shallow depth and a larger opening. Too much depth here just leaves the item rattling in a void.
Tall products
Bottles, candles, mugs — these need honest depth and usually a snug opening to hold them upright. Getting the depth right here does most of the protective work. If you’re still weighing up which style suits, our full range of box types is a useful place to compare shapes side by side.
A kitchen-table method
You don’t need special tools. A ruler or tape measure and two books will get you accurate numbers in a couple of minutes.
- Set the product on a flat surface.
- Stand a book upright against each end and measure the gap between them — that’s the length. Repeat across the shorter side for the width.
- For depth, stand a book beside the product and mark where the top reaches, then measure that height.
The books act as square edges so the ruler sits true, which is where casual measuring usually drifts. Note the three numbers, say whether they’re the product or the finished box, and you’ve got everything a printer needs to start.
If you can, measure twice on separate occasions and see if you get the same figures. It sounds fussy, but a soft product or a slightly tilted ruler can shift a number more than you’d expect, and a second pass catches it. Write the measurements down straight away rather than trusting memory between the table and the keyboard.
Getting it checked
If you’re unsure, send the product measurements rather than guessing at a box size — it’s easier to add the right clearance at our end than to correct a box that’s already made. A quick description of what’s going inside helps too, because a heavy item and a delicate one may want the same numbers but different board.
Once you’ve got your three figures, pass them over and we’ll turn them into a box built around your product.
