The Industry Standard: Why We Use Inside Dimensions (ID)
In the corrugated box industry, the Inside Dimension (ID) is the universal standard. When you order a box, the measurements provided always refer to the usable space inside the container.
We use ID for one primary reason: your product's fit. Because your goal is to house a specific item, the length, width, and depth of the internal cavity are the only measurements that guarantee your product will actually fit inside. Any deviation here—even by an eighth of an inch—can lead to damaged goods or wasted materials.
Why Carriers Care About Outside Dimensions (OD)
While manufacturers focus on ID, shipping carriers (like UPS, FedEx, or USPS) operate almost exclusively based on Outside Dimensions (OD).
Carriers care about OD because:
- Space Optimization: Their trucks and aircraft are finite spaces. They need to know the exact physical footprint of the box to maximize load efficiency.
- Dimensional Weight (DIM) Pricing: Carriers calculate shipping costs based on the space a package occupies rather than just its actual weight. If your box's OD is large, you may be charged at a higher "dimensional weight" rate, even if the item inside is lightweight.
Estimating Outside Dimensions: The Formula
To move from an Inside Dimension to an Outside Dimension, you must account for the thickness of the corrugated board. Because a box has two opposing walls for each dimension, you must multiply the board thickness by two to calculate the total exterior increase.
- Length & Width: Use the following formula to account for the thickness of the two opposing walls: OD = ID + (2 x Board Thickness)
- Height (Depth): This requires accounting for the box flaps. Since the flaps fold over to close the box, you must add the combined thickness of the top and bottom flap layers to your internal height. Effectively, this is also double the board thickness.
OD Height = ID Height + (2 x Board Thickness)
Note: For a standard C-Flute box, this adds approximately 0.32 inches. For heavier double-wall containers, this can be 0.5 inches or more.
Pro-Tips for Dimension Success
- Always Account for Flute: Different board grades have different thicknesses. Always confirm the board grade with your supplier before calculating your OD.
- Check the Stacking Orientation: Remember that for certain box styles, the length of the box can become the new vertical height in a stacking scenario, which directly impacts how carriers calculate your shipment's total footprint.
- Measure Twice, Order Once: If you are ever unsure about your OD vs. ID, contact our team in Vernon for a consultation. We can calculate the exact exterior footprint of your custom packaging to help you avoid surprise DIM weight surcharges.
Need a partner to navigate these technical specifications?
At Packaging & More, we specialize in helping businesses across the Los Angeles area optimize their packaging for both product protection and shipping efficiency. Contact us today for a professional packaging audit—we can even produce sample boxes so you can verify the dimensions before your production run!