Outside to inside dimensions calculator
Measured the outside of a box? Find the usable space inside it.
How it works
When all you have is a closed box, measuring the outside is easier. Subtract the board to find the space available for your product.
If you can open the box, measure the inside directly; it's more accurate than any formula because real board thickness varies. Then use the box size calculator to check whether your product plus cushioning fits.
Results are estimates based on typical industry values. Confirm final specifications with your supplier or carrier.
Frequently asked questions
Can I measure the inside of a closed box?
Not directly. Measure the outside and subtract the board thickness, or open one flap and measure wall to wall.
Why is my product not fitting a box that should be big enough?
Often the listed size was outside dimensions, or the width and height were swapped. Check the listing and measure the inside.
More box sizing and design tools
- Box dimensions converter
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- Inside to outside dimensions calculator
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Find a box's outer surface area and how much corrugated board it takes to make.
- RSC blank size calculator
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- Tuck end box blank size calculator
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- Mailer box size calculator
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