C flute: thickness, flutes per foot and strength
C flute is about 5/32 in thick with roughly 39 flutes per foot, between A and B in height. It is the general-purpose shipping flute: good stacking strength for its weight and acceptable crush resistance.
Key numbers
| Construction | Single wall: one medium, two liners |
|---|---|
| Nominal caliper | 0.1563 in · 4 mm |
| Flutes per foot | 39 ± 3 (128 per metre) |
| OD minus ID, length and width | 0.313 in |
| OD minus ID, depth | 0.469 in |
| McKee strength vs C flute, same ECT | 100% |
Strength ratio = √(caliper ÷ C-flute caliper), from the McKee formula with ECT and perimeter held equal.
Trade-offs
- Thicker than B, so stronger in McKee at the same ECT
- Fewer flutes per foot than B, so slightly less crush and puncture resistance
- Print surface is fine for simple marks; fine graphics prefer finer flutes
Typical uses
- Regular slotted shipping cases
- Boxes that stack on pallets in storage
Estimated box compression at 10 sizes
| Inside size, in | 23 ECT | 29 ECT | 44 ECT | 55 ECT |
|---|---|---|---|---|
| 8 × 6 × 4 | 282 | 356 | 540 | 675 |
| 10 × 8 × 6 | 320 | 404 | 613 | 766 |
| 12 × 12 × 12 | 370 | 466 | 707 | 884 |
| 14 × 10 × 8 | 370 | 466 | 707 | 884 |
| 16 × 12 × 10 | 399 | 504 | 764 | 955 |
| 18 × 12 × 12 | 413 | 521 | 791 | 989 |
| 18 × 18 × 18 | 453 | 571 | 866 | 1,083 |
| 20 × 16 × 14 | 453 | 571 | 866 | 1,083 |
| 24 × 18 × 18 | 489 | 617 | 936 | 1,170 |
| 24 × 24 × 24 | 523 | 659 | 1,000 | 1,250 |
BCT ≈ 5.87 × ECT × √(caliper × perimeter), perimeter = 2(L + W) of the inside size. An estimate; confirm with ASTM D642. Grades shown are ECT values Packgent computes for this wall type, not a list of what mills sell.
Sources
- Foster, G. (1997). "Boxes, Corrugated." In Brody & Marsh (eds.), The Wiley Encyclopedia of Packaging Technology, 2nd ed. Wiley. ISBN 0-471-06397-5 (table reproduced in Wikipedia, "Corrugated fiberboard")
- Packaging Corporation of America: Profiles with a purpose
Last reviewed . See all sources and how Packgent computes.