A box is always measured in this order: length × width × height, in cm. With the opening facing up, length is the longer side of the base, width is the shorter, and height is from the base to the opening. To know if your product fits, check the interior measurement.
Sounds simple, right? You grab the tape measure, measure, and that's it. Well, it's one of the most common mistakes we see: boxes that arrive and don't fit on the shelf, products that don't fit by half a centimeter, and orders returned because the order of the measurements was mixed up.
Measuring a box correctly has three rules. You can learn them in two minutes and they will save you trouble — and money, because the size of the box ends up defining what you pay for each shipment.
If you already know what you're looking for, here are our cardboard boxes in over 40 sizes.
Rule 1: the order is length × width × height
In the packaging industry, measurements are always given in this order: length × width × height (L × W × H).
With the box resting on its base and the opening facing up:
- Length: the longer side of the base.
- Width: the shorter side of the base.
- Height: from the base to the opening.
A "60×40×40" box measures 60 cm in length, 40 cm in width, and 40 cm in height. If you stand it "on its side" upon receiving it, your perception might change, but the nomenclature does not: the opening dictates the orientation.
Rule 2: interiors for the product, exteriors for shipping
Here is the half-centimeter that ruins orders.
A box's measurements can be interior (the usable space, what fits inside) or exterior (the space the assembled box occupies). The difference is the thickness of the cardboard: about 3-4 mm per wall in single-wall and 6-8 mm in double-wall. On a box, that easily adds up to 1-1.5 cm per dimension.
The practical rule:
- Do you want to know if your product fits? Check the interior measurements.
- Do you want to know how much you will pay for shipping or if it fits on your shelf? Check the exterior measurements — the courier always measures from the outside.
At TeleCajas, we indicate both measurements on each product page; if in doubt, ask us and we will confirm which one you need.
Rule 3: measure the product, don't guess
To choose a box, measure your product in its three maximum dimensions — including handles, caps, and protrusions — and add clearance depending on the case:
- Fragile product: add 2-3 cm per side for protective material. You have options in filling and protection.
- Resistant product (clothing, books): use a box that is as snug as possible. Less filling, less volume, lower cost.
- Multiple products per box: create a real layout on the table and measure the total arrangement. Mental calculations can be misleading.
The four mistakes we see every week
- Confusing the order and ending up with a box "on its side": 40×30×60 is not the same as 60×40×30.
- Measuring with the flaps open and including their height. Height should be measured with the box closed.
- Ignoring cardboard thickness when the fit is tight — the classic "it doesn't fit by 5 millimeters."
- Ordering by liters or volumes without checking dimensions. Two boxes with the same volume can hold very different things; if you need to calculate volumes, use our box volume calculator.
From the measurement to the specific box
With the three dimensions clear, choosing is easy: consult our guide to standard cardboard box sizes to see which size fits each use. And if the content is heavy, check first how much weight each type of box can hold.
Frequently asked questions
In what order are box measurements given?
Length × width × height, with the box resting on its base and the opening facing up. Length and width are the sides of the base (longer and shorter); height goes from the base to the opening.
Are box measurements interior or exterior?
It depends on the manufacturer, so check the product sheet. Interior measurements tell you what fits inside; exterior measurements tell you the space occupied. The difference is the thickness of the cardboard: up to 1.5 cm per dimension for double-wall.
How much clearance should I leave between the product and the box?
For fragile items, 2-3 cm per side for padding. For resistant products, the minimum possible: you pay for air in shipping, and internal movement causes more damage than impact.
What happens if the box is too big?
You pay more in volumetric weight, you waste more filler, and the package travels worse: the contents move, and a half-empty box is more easily crushed when stacked.
Doubts about your measurements?
Send us the measurements of your product via WhatsApp (+34 665 53 23 58) and we will tell you which of our more than 40 box sizes fits best. Delivery in 24-48 hours within the peninsula, Balearic Islands, and Portugal; free on orders over €50.
