How to measure a box for packaging?

Ordering custom packaging online can be tricky, especially when you’re unsure if the size is right. A box that’s too…

Yu Dai
December 12, 2024
A technician uses a yellow measuring tape to measure a sheet of cardboard and makes precise markings with a pen for custom box packaging.

Ordering custom packaging online can be tricky, especially when you’re unsure if the size is right. A box that’s too small risks damaging your product, while one that’s too big wastes space, money, and materials. No one wants to deal with the frustration of ordering the wrong size and having to start over.

That’s why getting your measurements right is so important. It’s about more than just convenience—it’s about confidence in your purchase.

This guide will help you measure boxes properly, calculate volume, and understand the difference between internal and external dimensions. With these tips, you’ll know exactly what you need and can order packaging online without second-guessing. Let’s make sure your next box is the perfect fit.

How to measure a box demension?

The images depict a custom packaging box with key dimensions indicated: width (W), length (L), and height (H). The first image presents the box in its closed form, while the second shows it partially open. These visuals illustrate the structural aspects of our custom packaging solutions without referencing specific text on the box itself.

The industry standard follows a specific order: Length x Width x Height (L x W x H). Here’s how to measure each dimension:

Length: Start with the longest side of the box. Measure it from end to end using a      ruler or tape measure. This is typically the front panel of the box.

Width: Measure the shorter side of the box that is perpendicular to the length. This is usually one of the side panels. Be precise and measure edge to edge.

Height: Measure the distance from the base of the box to its top. This is the vertical measurement, also referred to as the depth.

Tip: Always record all measurements in the same units, such as inches or millimeters, to maintain consistency and avoid errors in calculations or orders.

By following these steps, you’ll ensure precise measurements for efficient use of space and materials.

How to Calculate Box Volume

Box volume is the amount of space a box occupies, calculated using the formula:

LxWxH

For example, if a box measures 10 inches (L) × 5 inches (W) × 4 inches (H):

10 × 5 × 4 = 200 cubic inches

Volume is crucial for shipping, as many companies calculate costs based on volumetric weight, especially for lightweight but bulky boxes. Accurate volume measurement helps determine shipping charges and optimize space usage.

Converting Units: Millimeters to Inches

It’s important to keep your units consistent. In the U.S., measurements are usually given in inches, but packaging designs often use millimeters (mm). To convert millimeters to inches, use this formula:

Inches = Millimeters ÷ 25.4

For example:

  • 100 mm ÷ 25.4 = 3.94 inches
  • 500 mm ÷ 25.4 = 19.69 inches

Tip: Use a unit converter or online tool to save time and ensure accuracy.

External VS Internal Box Dimensions

External Dimensions


Most packaging manufacturers communicate using external dimensions. These measure the outside of the box, including the thickness of the material. External dimensions are especially important for shipping, as carriers use them to calculate volumetric weight and optimize space during transport.

Internal Dimensions


Internal dimensions are the measurements inside the box. It ensures your product fits securely without damaging the packaging or the item itself.

Are external dimensions enough?


Yes, in most cases, external dimensions are enough. 

However, for thicker materials like corrugated boxes, you need to measure both. Corrugated boxes are made with a fluted layer between two paperboards, adding a few millimeters to the overall size. Measuring both internal and external dimensions ensures the box works well for your product while meeting shipping requirements.

Taking the time to measure correctly prevents fit issues, protects your product, and keeps shipping costs predictable.

Next Step

By following these simple steps, You’re now equipped with the knowledge to measure boxes confidently and accurately. 

<= 48 H
You will receive the dieline
WITPAX dieline

If you’re ready to take the next step, simply fill in the measurements. With your exact specifications, WITPAX packaging team will create packaging that fits your products.

No guesswork, no hassle—just the right fit for your products and your business.

One Click Away

Measuring boxes is simple enough, but what about irregular products like sunglasses or tubes of face cream? That’s where things can get tricky—but we’re here to help!

With our easy-to-follow guide, you’ll learn how to measure even the most uniquely shaped items accurately. Whether it’s a rounded edge or a cylindrical tube, we’ll show you exactly what to do to find the perfect fit for your packaging needs.

Click here to check out the guide and get started!