Difference between Internal and External Measurements

Internal measurements are the usable space inside the box, essential for fitting and protecting contents.  When providing measurements for a custom box, the internal dimensions are used for manufacturing. We take the internal dimensions and score, slot and cut the box with tolerances based on the board thickness selected to ensure the internal dimensions remain your specified measurement.

External measurements are concerned with the overall size of the box, which impacts shipping, storage, and handling but are not used for manufacturing. Please ensure you provide your measurements as internal dimensions only.

Measuring your Box in Millimetres

In Australia, millimetres are preferred for box size manufacturing primarily due to the metric system’s adoption, which standardises measurements across industries. Using millimetres allows for greater precision and consistency, which is essential in manufacturing processes where exact dimensions can impact product quality and efficiency.

Practical Example

Consider a scenario where you need to ship a fragile electronic device: 

• Internal Measurements: Ensure the device fits snugly with adequate padding to prevent movement and damage during transit.
• External Measurements: Ensure the package meets the shipping carrier’s size restrictions and optimises shipping costs based on dimensional weight.

By understanding both internal and external dimensions, you can make informed decisions about packaging, shipping, and storage, ensuring efficiency, cost-effectiveness, and the safety of your items.

Steps to Measure the Internal Dimensions of a Box

To measure the internal dimensions of a box, follow these steps:

Materials Needed

1. Measuring tape or a ruler
2. Notepad and pen/pencil (to record the measurements)
3. Flashlight (optional, for better visibility inside the box)

Step 1: Open the Box

1. Ensure the box is empty. Remove any contents inside the box to avoid obstruction.
2. Fully open the flaps or lid to have unobstructed access to the internal space.
3. If the box is glued inside, carefully unstick the glue flap so the box can lay flat on a clear surface, with the outside of the box facing down.

 Step 2: Measure the Length

1. Locate the longest side of the inside of the box. This is the length.
2. Position the measuring tape or ruler at one end of the inside edge of the box, in the centre of the score (this is the indented crease).
3. Extend the measuring tape or slide the ruler across the box to the other end of the inside edge in the centre of the score.
4. Record the measurement. Write down the length in millimetres

Step 3: Measure the Width

1. Locate the shorter side of the inside of the box. This is the width.
2. Position the measuring tape or ruler at one end of the inside edge of the box, in the centre of the score (this is the indented crease).
3. Extend the measuring tape or slide the ruler across the box to the other end of the inside edge.
4. Record the measurement. Write down the width in millimetres.

 Step 4: Measure the Height

1. Position the measuring tape or ruler at the bottom inside score of one of the vertical sides of the box.
2. This should be measured from score to score only and not include the measurement of any flaps.
3. Extend the measuring tape or slide the ruler upwards to the top inside edge of the box.
4. Record the measurement. Write down the height in millimetres.

 Tips for Accurate Measurements

• Double-check each measurement to ensure accuracy. Measure again if necessary.
• Keep the measuring tape straight and avoid bending it to get an accurate measurement.
• By following these steps, you will obtain precise internal measurements of any box.

Download Our Handy Guide

For your convenience, we’ve compiled all this information into a handy downloadable guide.

How To Measure A Box Guide

Download our comprehensive "How to Measure a Box" guide now and ensure your items fit perfectly every time.