Almost everyone has ordered a cardboard box once and got one completely wrong size. You measure your item, order the exact same number, and the box arrives too small. This happens because almost no one tells you how cardboard box dimensions actually work. Almost every website and box seller skips the single most important part. This article has no tricks. It will tell you exactly how it all works.

How Are Cardboard Box Dimensions Actually Measured?

This is the secret that no one tells you. All cardboard box dimensions are always measured on the inside of the box. Never the outside. Most people assume the dimensions of cardboard box is the size of the outside. This is wrong. This is the number one mistake that 9 out of 10 people make. You will see almost every cardboard box with dimensions printed on the bottom. That number is always internal.

Standard Cardboard Box Dimensions

There is no official global standard but almost all manufacturers use the same sizes all over the world. All sizes follow one single rule that never changes. They are always listed in the exact same order. Length first, then width, then height. Always. If you mix up this order you will get the wrong box every single time.

Cardboard Box Dimensions In Inches

In the United States and Canada all standard cardboard box dimensions in inches use this order. The most common general purpose size is 12x9x6 inch. This is the size you will find in almost every post office.

Cardboard Box Dimensions Cm

In all other countries standard sizes are listed as cardboard box dimensions cm. The order remains exactly the same. Length, width, height. There is no difference in how they are measured, only the unit used.

Small Cardboard Box Dimensions

Small cardboard box dimensions are any size under 12 inch or 30cm long. These are used for phones, books, small parts and jewellery. The most common small size is 8x6x4 inch.

Medium Cardboard Box Dimensions

Medium cardboard box dimensions are between 12 and 24 inch or 30 and 60cm. This is the most used size for shipping and moving. All courier services give the best price for medium size boxes.

Large Cardboard Box Dimensions

Large cardboard box dimensions are any size over 24 inch or 60cm long. Be very careful with large boxes. They get extremely expensive to ship very quickly once they go over 30 inch on any side.

Carton Box Dimensions For Shipping

Courier services have very strict hidden rules about carton box dimensions. Most will charge you a very large oversize fee if any side is over 48 inch, or if you add all three sides together and the total is over 105 inch. This fee is usually 3 or 4 times the normal shipping cost. Almost no one knows about this fee until they get the bill. These rules apply to all cardboard box sizes for shipping with every major courier service in the world.

Common Mistakes To Avoid

Always add a little extra space. If your item is exactly 10 inch wide do not order a 10 inch box. Order 10.5 inch. If you use bubble wrap add one full inch extra. Never guess. If you need a box to fit inside a shelf or a car you have to ask for external dimensions specifically. Almost no seller will give you this information unless you ask directly.

When you need any size made exactly to your exact measurement you can order custom cardboard boxes from We Custom Boxes made to any size you need.

How To Order The Correct Size Every Time

Follow this very simple step and you will never get the wrong box again. First measure your item. Add half inch if you use paper wrap. Add one full inch if you use bubble wrap. That number is the size you order. Do not add more. Do not add less. This works 99% of the time. If your item is very heavy add one and half inch instead. That is all. There is no secret trick.

Conclusion

So cardboard box dimensions are not complicated once you know the simple unwritten rules. Almost all the confusion comes from sellers who do not tell you they measure internal size. Always remember the order length width height. Always add a little extra space. Always check the courier size limit before you order. Now you will never order the wrong size box ever again.