A flute vs C flute: side-by-side numbers
C flute is 17% thinner than A flute (0.156 vs 0.188 in nominal). At the same ECT, the McKee formula rates a C flute box 9% weaker in compression; the trade is in size, crush resistance and print surface.
Side by side
A flute is 0.031 in thicker than C flute. On a 12 × 10 × 8 in box that makes the outside 0.06 in longer and wider and 0.09 in deeper, and at the same ECT the McKee estimate for C flute is 91% of the A flute figure.
Same box, both boards
| Inside, in | BCT at 44 ECT, A | BCT at 44 ECT, C | Boxes per pallet, A | Boxes per pallet, C |
|---|---|---|---|---|
| 10 × 8 × 6 | 671 | 613 | 144 | 144 |
| 16 × 12 × 10 | 837 | 764 | 40 | 40 |
| 24 × 18 × 18 | 1,025 | 936 | 6 | 6 |
44 ECT is used on both sides only to isolate thickness; in practice the two boards are made to different grades. Pallet: 48 × 40, loaded to 60 in, column stacked.
Where each fits
A flute
- Thickest single wall, so the best McKee estimate at a given ECT
- Tall flutes crush more easily under flat pressure, which can cost some of that strength on a corrugator or in a clamp truck
- Less common in US box plants than B or C; check availability before you specify it
C flute
- 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
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
- McKee, Gander & Wachuta (1963), Paperboard Packaging 48(8)
Last reviewed . See all sources and how Packgent computes.