Sizing guide
Box dimensions explained: inside vs outside
“250 × 180 × 60 mm” is incomplete until you say what the numbers measure. The same numbers can describe three different boxes.
Calculate your box size
From flat to finished.Quick answer
Inside dimensions describe usable room for the product. Outside dimensions describe the finished box footprint. Score-to-score dimensions measure between crease centres on the flat blank. Board thickness and folded wall layers make these values different; specify the convention alongside L × W × H.
Three measurements, three jobs
Inside size is the space available for the product and insert. Outside size matters when cartons must fit a shelf, shipping case, or pallet pattern. Score-to-score is the flat distance between creases that a converter uses to build the cutting die. These are related measurements, not interchangeable labels.
A straightforward single-wall carton gains roughly one board thickness on each side as it goes from inside to outside. Mailers with rolled walls and rigid boxes with wrapped construction behave differently. Use the actual structure and material to calculate the allowance.
| Dimension | Measured where | Use it for |
|---|---|---|
| Inside | Clear space within the assembled walls | Product fit and insert design |
| Outside | Full size of the folded pack | Shelf, shipper, and storage fit |
| Score-to-score | Between crease centres on the flat blank | Die and converter setup |
A quick example
Suppose a product needs 250 × 180 × 60 mm of inside room. In 0.5 mm carton board, a simple single-wall construction may be about 251 × 181 × 61 mm outside. Replace that board with corrugated material or use double-folded mailer walls and the difference grows. The exact result depends on how the chosen structure folds.
Do not add a fixed allowance to every style. Choose the actual structure and board, enter the dimension you know, and calculate the other two from the same blank.
Calculate all three box sizesWhat to put on the brief
Write “inside L × W × H,” the board grade and caliper, and the product clearance you need. If outside fit is constrained, state that maximum as well. Send a drawing or a sized dieline so the opening direction and wall construction are clear.
A sample remains the final check. Board tolerance, print, lamination, and manufacturing setup can all change fit in ways a clean digital model cannot feel.
Measure the product
Include protrusions and insert thickness.
Pick a box structure
The wall construction determines how board caliper accumulates.
State the convention
Label the dimension as inside, outside, or score-to-score.
Confirm with a sample
Check insertion, closure, and external fit before a run.
Common questions
Does box length include the board thickness?
It depends on the stated convention. Inside length excludes the walls; outside length includes them. Score-to-score measures a crease span on the blank.
Which dimensions do most box makers ask for?
Inside L × W × H is a common starting point, but confirm the supplier’s convention. If a drawing or quote says manufacturer’s size, ask whether it means score-to-score.
How much clearance should I leave?
Enough for the product and any insert to enter without forcing. A few millimetres can be sufficient for a simple folding carton; fragile, irregular, or corrugated packs may need more. Test a sample.
Put it into practice.
Start with the structure, check the fold, and make the file your printer needs.
Calculate your box size