Box blank size calculator
Get the flat blank size and board area for any slotted style from its inside dimensions and flute.
Calculator
45.88 × 18.31 in
5.83 ft² of board per box
| Nominal length 2L + 2W + 1.25 | 45.25 in |
|---|---|
| Nominal width H + flaps | 18 in |
| Outer flaps top / bottom | 5 / 5 in |
| Inner flaps top / bottom | 5 / 5 in |
| Score allowance (0.156 in per score) | +0.625 / +0.313 in |
How it works
- Blank length = 2L + 2W + glue tab (1¼ in), plus one caliper per vertical score.
- Blank width = H + top flap + bottom flap, plus one caliper per flap score. Flap lengths follow each style's rule.
- Area in ft² = length × width ÷ 144.
Results are estimates for planning. Confirm critical packs by test. Full method.
Reading the result
The blank is the flat sheet the box is cut from, so its area drives board cost. Two styles with the same inside size can need very different blanks: a full-overlap box uses far more board in its flaps than a regular slotted box.
Use the area with your board's combined weight in the box weight tool to estimate how much an empty box weighs, or to compare board use between styles.