Measurement guide
Measure the product. The box follows.
Almost every avoidable problem in a corrugated request comes from three numbers that were measured in the wrong place. This page covers where those numbers come from, why a box is always specified from the inside, and how much space to leave around what you are packing.
This guide is illustrative and is not an engineering certification.
01 — The one that matters
Internal, not external.
A corrugated box has thickness. The internal dimension is the usable space your product actually occupies. The external dimension is that space plus the board on both walls, and it is what matters to whoever has to stack, palletise or ship the finished carton.
Specifications are written as internal dimensions, because the internal dimension is the one that has to fit the product. The external size is then a consequence of the board that is selected during review.
If the only measurement available to you is an external one — for example taken from a box already in use — send it anyway and label it clearly as external. It is far better to state which one you measured than to convert it yourself.
02 — Taking the measurement
Three numbers, always in the same order.
- L
Length
Face the box the way it opens. Measure the longer of the two sides across that opening. On a regular slotted carton this is the side the outer flaps run along.
- W
Width
Measure the shorter side across the same opening, at right angles to the length. Width and length together describe the footprint the product sits on.
- H
Height
Measure from the opening straight down to the inside of the base. Height is also called depth. It is the axis that changes when you stack more than one item per box.
Measure with a rigid rule against a flat surface rather than a tape held in the air, and measure the product itself rather than its retail packaging unless the retail packaging is what goes in the box.
03 — Product size plus clearance
The product decides the box, not the other way round.
A box sized exactly to the product cannot be loaded. Every internal dimension is the product dimension plus a clearance allowance on each of the two opposing walls, so a 10 mm allowance adds 20 mm across the length and the same across the width.
How much clearance is right depends on what is actually going in. A rigid item placed by hand needs very little. An item that will be wrapped, or that needs void fill or an internal insert around it, needs considerably more. Extra clearance is not free: it increases the sheet area of every box and it increases the volume you ship.
Step 1 — Your product
Measure the item you intend to pack, not a box you already have. If several identical items go into one box, enter the size of one item and set the count below.
The longest side of the product as it will sit in the box.
The shorter side measured across the same face as the length.
The depth of the product from that face downwards.
All three sides use the same unit.
Step 2 — How many per box
This guide stacks the items one on top of another, so only the height changes.
Step 3 — Clearance
Clearance is the free space between the product and the inside wall of the box. It covers getting the product in and out. It is not a cushioning calculation.
Suggested internal box size
Enter a length, width and height to see a suggested internal box size.
This guide is illustrative and is not an engineering certification. Packaging requirements vary according to product and handling conditions.
04 — Before you send
Six things worth checking.
None of these are difficult. All of them are easier to correct before a quotation is prepared than after.
Next step
Let's Build the Box Around Your Product.
Send your required dimensions, quantity, printing, and handling specifications for quotation review.