Corrugated Grade Types


Corrugated board consists of two, paper-based flat boards with a wavy, or fluted, layer in the middle. It is commonly used to make strong boxes and shipping containers. Different types are rated using strength tests.

Burst Test

  • The burst test measurement is stated in pounds per square inch and measures how a box can stand up to internal and external forces against hydraulic pressure. Some types include 200 test, 275 test and 350 double-wall, the strongest. Burst test board is considered stronger and higher quality than boards which have not been tested.

Edge Crush test

  • The edge crush test (ECT) tests how much pressure is needed to crush a box from top to bottom. A box with 32 ECT means it can stand 32 pounds per square inch without compression.

Paper Grades

  • The outer and inner lining sheets also have grades. Some examples are K (Kraft), made from virgin Kraft paper, T (Test 3) for fully recycled paper, and C (Chip) for waste-based liners.

Flute Sizes

  • The fluting in between the liners has a corresponding letter grade. It ranges from A to F with A being the thickest. The most common grades are B and C.

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