How to measure a box (and why your first one is usually wrong)

Box dimensions are written length x width x depth, they’re always the inside measurements, and length is always the longer side of the opening. If you remember nothing else from this page, remember those three things. Most sizing problems come from getting one of them wrong.

Which side is which

Put the box in front of you with the opening facing up. Now look down into it.

• Length is the longer of the two sides of that opening.
• Width is the shorter side of the opening.
• Depth is how far down it goes from the opening to the base.

So a 10 x 8 x 4 box has a 10 inch by 8 inch mouth and sits 4 inches tall. Flip those numbers around and you get a completely different box. We’ve had people order a 4 x 8 x 10 when they wanted a 10 x 8 x 4, and the boxes are useless for the product either way.

Inside, not outside

Every dimension you give a printer should be the internal space your product sits in. Board has thickness, and on a corrugated box that thickness isn’t trivial.

Two walls of B flute eat about a quarter inch off your outside measurement. That sounds like nothing until your product is 6 inches wide and you ordered a 6 inch box measured from the outside. It won’t go in.

How much room to leave

Measure your product at its widest point, including anything that sticks out. A pump, a lid, a handle, the seam on a pouch. Then add clearance:

• 1/8 inch total if the product is rigid and you want it snug, like a rigid box holding a single item.
• 1/4 inch total for most things. This is the sensible default.
• 1/2 inch or more if the product is soft, wrapped in tissue, bagged, or going in with void fill.

Tighter than an eighth and you’re relying on the box being perfect, which it won’t be. Corrugated has a manufacturing tolerance of around 1/16 inch, so a box that fits only in theory will fail on part of the run.

A worked example

Say you sell a candle. The glass is 3 inches across and 4 inches tall, and you wrap each one in tissue.

• Widest point: 3 inches, call it 3.25 with the tissue.
• Add a quarter inch of clearance: 3.5 inches.
• Height: 4 inches, plus a little so the lid isn’t resting on the glass: 4.25.

So you’re looking at a 3.5 x 3.5 x 4.25 inch internal box. In practice we’d round to 3.5 x 3.5 x 4.5 and add a corrugated insert, because a candle that can shift in transit is a candle that arrives broken.

The most common measuring mistakes

1. Measuring an existing box from the outside. If you’re copying a box you already like, open it flat and measure the inside faces, or tell us the brand and style and we’ll work it out.
2. Measuring the product, not the packed product. The thing that goes in the box is your product plus tissue plus a card plus a sticker. Measure that.
3. Forgetting the box has to close. On a mailer, the front flap needs to tuck down inside. Overstuff it and the flap pops open in transit, every time.
4. Ordering for one product when you have four. If your range varies in size, it’s almost always cheaper to pick two box sizes that cover everything than to run four.
5. Ignoring the shipping cost. Carriers charge on dimensional weight. An inch of unnecessary depth across 500 shipments costs real money, often more than the boxes did. Our shipping box size chart shows which sizes stay under each USPS cubic price tier.

What to send us

Honestly, you don’t have to do any of this. Send us the product dimensions, or send us the product, and we’ll spec the box. If you’d rather work it out yourself first, the pricing guide has an estimator that will give you a ballpark once you have a size in mind, and the free dielines let you print a flat template and fold it in paper before you commit to a run.

One more thing worth saying: order a sample before you order 500. We do free sample packs partly because it’s the cheapest way for both of us to find out that a box is an eighth of an inch too tight.