12 × 9 × 4 in box: dimensions, dim weight and strength
A 12 × 9 × 4 in box holds 432 in³ (0.25 ft³) inside. Made in C flute its outside is about 12.31 × 9.31 × 4.47 in, which dimensional weight bills USPS at actual weight (under its threshold) and FedEx at 4 lb.
Key numbers
| Inside (L × W × H) | 12 × 9 × 4 in |
|---|---|
| Inside volume | 432 in³ · 0.25 ft³ · 7.1 L |
| Inside, metric | 305 × 229 × 102 mm |
| Perimeter 2(L + W) | 42 in |
| Length + girth, C flute OD | 39.9 in |
Outside dimensions by flute
| Board | Caliper, in | Outside, in | Outside volume, ft³ |
|---|---|---|---|
| E flute | 0.063 | 12.13 × 9.13 × 4.19 | 0.268 |
| B flute | 0.125 | 12.25 × 9.25 × 4.38 | 0.287 |
| C flute | 0.156 | 12.31 × 9.31 × 4.47 | 0.297 |
| EB double wall | 0.188 | 12.38 × 9.38 × 4.56 | 0.306 |
| BC double wall | 0.281 | 12.56 × 9.56 × 4.84 | 0.337 |
OD ≈ ID + 2 calipers on length and width, + 3 on depth. An estimate: your box maker sets the scores. Convert other sizes.
Dimensional weight
| Carrier | Divisor | Measured, in (C) | DW, C flute | DW, BC double wall |
|---|---|---|---|---|
| USPS | 139 | 13 × 10 × 5 | n/a | n/a |
| FedEx | 139 | 12 × 9 × 4 | 4 lb | 5 lb |
DW = ⌈L × W × H ÷ divisor⌉ on outside dimensions, after each carrier's own rounding. USPS applies it only above 1,728 in³ (n/a means it bills actual weight). The carrier bills the greater of actual and dimensional weight. Divisors checked on carrier pages 2026-10-27; try your own weight.
Estimated compression strength
| Board | BCT, lbf | After 30 days storage |
|---|---|---|
| 32 ECT B flute | 430 | 258 |
| 32 ECT C flute | 481 | 289 |
| 44 ECT C flute | 662 | 397 |
| 48 ECT C flute | 722 | 433 |
| 48 ECT BC double wall | 968 | 581 |
| 61 ECT BC double wall | 1,231 | 738 |
| 71 ECT BC double wall | 1,433 | 860 |
Simplified McKee: BCT ≈ 5.87 × ECT × √(caliper × 42). The 30-day column applies Packgent's default 40% storage loss, an assumption. Estimates only; test with ASTM D642.
Pallet pattern on 48 × 40
| Board | Per layer | Layers | Boxes per pallet | Load height, in | Cube used |
|---|---|---|---|---|---|
| C flute | 15 | 12 | 180 | 59.1 | 88% |
| BC double wall | 15 | 11 | 165 | 58.8 | 92% |
Column stacked, no overhang, on a 48 × 40 in deck 5.5 in tall, loaded to 60 in overall. Those three are assumptions you can change in the pallet calculator. Pattern: 9.3125″ along the 48″ side.
Blank size in C flute
With one caliper allowance per score. Multiply board area by your board's combined weight (lb/MSF ÷ 1,000) for box weight, or use the box weight calculator.
Sources
- USPS Domestic Mail Manual 223 (Priority Mail prices and eligibility), section 1.4
- FedEx: What is dimensional weight?
- Flute calipers: Foster (1997), Wiley Encyclopedia of Packaging Technology
- McKee, Gander & Wachuta (1963), Paperboard Packaging 48(8)
Last reviewed . See all sources and how Packgent computes.
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