How to Measure Custom Boxes

The correct box size ensures your products fit properly, your packaging works as intended, and your shipping costs stay low. In many cases, choosing the right dimensions can save your business significant money on freight, storage, and fulfillment.

This guide covers everything you need to know to measure boxes correctly, whether you are submitting a custom box order or checking the fit for your products.

WHAT ARE YOU MEASURING?

There are two types of box measurements used in packaging: exterior dimensions and interior dimensions.

Exterior Dimensions

Exterior dimensions describe the outside size of your box.

These measurements help you determine:

How much room a box will take up in storage
How it fits inside a larger shipper or case pack
How carriers calculate shipping costs

Interior Dimensions

Interior dimensions describe how much usable space is inside the box.

These measurements are used when placing a custom box order.

Interior dimensions determine:

Whether your product will fit properly
How much void fill you will need
How stable the product is during transit

Because materials and structural folds take up space, interior and exterior dimensions are not the same. Always use interior dimensions when ordering a custom box.

UNDERSTANDING LENGTH, WIDTH, AND DEPTH

When measuring any box, these three terms always refer to the same positions:

Length – Left to right measurement
Width – Front to back measurement
Depth – Bottom to top measurement

HOW TO MEASURE AN EXISTING BOX

Measurements should be taken with a rigid ruler or tape measure on a flat surface.

Exterior Dimensions

Close the box completely.
Place it on a flat surface with the top panel facing up.
Measure the length from left to right.
Measure the width from back to front.
Measure the depth from the bottom surface to the highest point on the top panel.

Interior Dimensions

Open the box and remove all the contents.
Place it upright on a flat surface.
Measure the length from the inside of the left panel to the inside of the right panel.
Measure the width from the inside of the front panel to the inside of the back panel.
Measure the depth from the inside of the bottom panel to the inside of the top panel.

HOW TO MEASURE YOUR CONTENTS TO CHOOSE THE RIGHT BOX SIZE

To ensure your packaging fits, measure your product exactly as it will be arranged inside the box.

Gather everything that will go inside the box, including void fill such as tissue paper, crinkle fill, or bubble wrap.
Arrange all items on a flat surface in the packing position.
Measure the length at the widest point from left to right.
Measure the width from back to front, again at the widest point.
Measure the depth from the flat surface to the tallest item.
Add 0.125" to 0.25" to each dimension to allow room for packing and easy unboxing.

This extra allowance ensures the product fits comfortably and prevents stress on the box walls during assembly.

NEED HELP?

If your product has an irregular shape or requires special protection, or if you want to create custom inserts or a unique unboxing experience, our Packola packaging experts can help.

We can:

Recommend the best box style
Review your measurements
Create custom inserts
Suggest the correct flute, size, or material
Help develop a fully custom structure