C flute is a corrugated board profile. The fluted middle layer is sandwiched between two liners, and the flute profile describes how tall and how frequent those corrugations are. C flute sits in the middle of the common range at roughly 5/32 in (about 4 mm) caliper and around 41 flutes per foot, which is why it became the standard shipping board for most of North America.
Where C flute sits in the range
These are published industry-typical figures. Individual mills vary slightly, so treat them as the working reference rather than an exact specification.
| Flute | Approximate caliper | Approximate flutes per foot | Character |
|---|---|---|---|
| A | about 1/4 in (6.4 mm) | about 36 | Most cushioning, bulkiest, poorest print surface |
| C | about 5/32 in (4 mm) | about 41 | The general purpose shipper, good stacking and cushioning |
| B | about 1/8 in (3.2 mm) | about 49 | Flatter face, better crush resistance, less cushioning |
| E | about 1/16 in (1.6 mm) | about 90 | Retail board, prints close to folding carton quality |
| F | about 1/32 in (0.8 mm) | about 128 | Thin retail board for small, light, highly printed cartons |
C flute against B flute, the decision most people are actually making
Almost nobody is choosing between C and A. The real fork is C or B for a shipping carton. C flute has taller flutes, so it absorbs more shock and holds a taller stack. B flute has more flutes per foot supporting the liner, so it resists flat crush better and gives a smoother printing face. If your product is fragile and the carton will be stacked in a warehouse, C usually wins. If the carton is highly printed, or it will be handled individually and pressed rather than stacked, B often wins. If you need both, double wall combines them.
What C flute does to your dimensions
Flute choice is a sizing decision, not only a strength one. The board thickness sits between your product and the outside world, so every wall adds one caliper. A C flute box with a 10 x 10 in internal footprint runs about 10 5/16 in externally on both axes. Over a 48 x 40 in pallet that can be the difference between fitting a column and overhanging it. Always state on your quote whether the dimensions you gave are internal or external.
What C flute does not tell you
Flute is only half of a board specification. The liners, their weight and the overall board grade decide how much load the finished box carries. Two C flute boxes from different board grades are not equivalent. So specify the flute for the size and feel you want, and then describe the real job: the product weight, how high it will be stacked, and how far it travels. That is what lets a board be matched properly rather than guessed.
Ordering
Minimum order is 100 boxes. Price starts from about $0.48 per unit at bulk volumes and is confirmed on your written quote, because flute, liner grade, print coverage and finishing all move it. The cutting die, the plates, design support, US shipping and a digital proof before anything prints are included. Production comes from West Chicago in the US and Guangzhou in China in three lanes: rush (expedited production plus air freight, a premium of about 7 to 25% depending on the job), standard (air) and cost saver (sea). The floor is from about 7 business days, plus 2 to 5 for delivery.
If C flute is not enough for your load, double wall box dimensions covers the next step up and what it does to your internal size. Stock shipping styles are on the corrugated boxes page. Send your internal dimensions, your product weight and how it will be stacked through the quote form, and ask for a B flute and a C flute version priced together so you can see what the difference actually costs.
