What is the difference between internal, external, and score-to-score box dimensions?

When engineering custom packaging, three distinct dimensional benchmarks exist:

### 1. Internal Dimensions (Usable Cavity):

• The internal usable space inside the closed box ( \times W \times D$).


• Importance: This is what prevents your product from being crushed. Always quote internal dimensions to packaging suppliers.

### 2. External Dimensions (Shipping Footprint):


• The total outer boundary of the closed box including board thickness, folds, and corners.


• Importance: Used by couriers (Royal Mail, DPD, FedEx) to calculate volumetric shipping charges.

### 3. Score-to-Score Dimensions (Structural Engineering):


• The exact distance between crease score lines on flat 2D die-cutting sheets.


• Calculation: Structural CAD designers calculate score allowances based on board caliper (e.g., adding half the board thickness on each fold) so the folded 3D box achieves the exact desired internal cavity.