Sizes & specs · board
Wall count is shorthand. Ratings are the truth.
- Common in gaylords
- 4-wall and 5-wall
- Common in octabins
- Triple wall
- Ask for
- Payload, not just wall
Match a board spec
Know your ECT or Mullen requirement? Put it in Message and a partner supplier follows up. Availability depends on partner suppliers.
Answer first
Two numbers tell you almost everything.
Edge Crush Test (ECT), in pounds per inch, predicts how much load the box carries when stacked. Mullen burst, in pounds per square inch, predicts how much abuse it takes before something goes through it. Stacking in a warehouse is an ECT problem. Forklifts, dragging and rough yards are Mullen problems.
Wall count correlates with both but guarantees neither, because manufacturers combine flute profiles and liner weights differently. That is why it pays to ask a supplier for a payload figure derived from the board spec and derated for observed condition, not simply copied off a stamp.
The ladder
Five constructions, from carton to bulk container.
| Construction | Plies | ECT range | Mullen | Typical payload | Notes |
|---|---|---|---|---|---|
| Single wall | 1 flute layer, 2 liners | 32 – 48 lb/in | 200 – 275 psi | Up to 65 lb | Shipping cartons, not bulk boxes. Usually handled by the bundle or bale, rarely used as gaylords. |
| Double wall | 2 flute layers, 3 liners | 48 – 71 lb/in | 275 – 500 psi | 65 – 120 lb | Heavy shipping cartons and small bulk bins. The lightest board that survives a forklift near-miss. |
| Triple wall | 3 flute layers, 4 liners | 67 – 112 lb/in | 700 – 1,300 psi | 700 – 1,500 lb | The classic octabin and shallow tray board. Excellent stacking, less tolerant of repeated re-folding. |
| 4-wall (double-wall sleeve, doubled) | Two double-wall sleeves nested or a 4-ply construction | 90 – 120 lb/in | 1,100 psi+ | 1,200 – 1,800 lb | A very common used gaylord. Good all-round reuse candidate: stiff and repairable. |
| 5-wall | Triple wall plus an extra liner and flute | 110 – 160 lb/in | 1,300 psi+ | 1,800 – 2,500 lb | Heavy industrial standard. Survives the most reuse cycles and holds squareness after several trips. |
Flutes
What the corrugations actually do.
| Flute | Height | Flutes per foot | Strength character | Where it appears |
|---|---|---|---|---|
| A | ≈ 3/16 in | 33 – 36 | Best vertical compression and cushioning | Outer plies of bulk boxes and octabins |
| B | ≈ 1/8 in | 47 – 53 | Best puncture and crush resistance | Inner plies, shipping cartons |
| C | ≈ 5/32 in | 38 – 42 | General-purpose compromise | The most common single-wall shipping board |
| E | ≈ 1/16 in | 90 – 96 | Fine surface, printable, low strength | Retail and point-of-sale packaging |
| BC / AC double | Combined | — | Combines puncture and compression | Double wall cartons and 4-wall gaylords |
| AAC / ABC triple | Combined | — | Maximum industrial strength | Triple and 5-wall bulk containers |
Reading a box
The certificate stamp, decoded.
The round stamp on a bottom flap — the box certificate — is the manufacturer's declaration. It states whether the box is rated by burst or by edge crush, the value, the maximum size in combined inside dimensions, and the gross weight limit.
On used boxes it is frequently scuffed, overprinted or missing entirely. Treat it as evidence rather than authority: where it is legible, note it, and where it is not, the box can be rated from construction, measured board thickness and condition. A supplier quoting purely from a stamp on a five-year-old box is quoting a number nobody has verified since the day it was printed.
Questions
Board strength, answered.
What is the difference between ECT and Mullen ratings?
How many walls does a gaylord box have?
Which flute profile is used in bulk boxes?
Where do I find the specification on a used box?
Choosing board
Work backwards from the load, not forwards from the catalogue.
Five inputs decide the construction. Get these and the board specifies itself — which is why they are better to quote than a wall count.
- 01
Loaded weight per container
Weighed, not designed. Actual loads often run below the figure the specification was built around, which can mean a wall grade down and a lower cost.
- 02
Stack height, loaded
One high needs nothing special. Two high needs the derated compression figure. Three high needs five-wall, dry storage and disciplined alignment — it is a decision, not an assumption.
- 03
Storage duration
Creep is cumulative and largely irreversible. The longer a loaded stack sits, the more strength it loses, so apply a bigger safety factor for longer storage. Rotating stock is cheaper than upgrading board.
- 04
Ambient humidity, honestly
Not the specification figure, the worst-month figure. Board loses a good share of its compression strength in high humidity, and no wall count fully compensates for that.
- 05
Handling roughness
Forklift contact, dragging and yard moves are a burst-strength problem rather than a stacking problem. If the box gets abused rather than stacked, Mullen matters more than ECT.
Reference
Board terminology, decoded.
The vocabulary on a specification sheet, in plain language, with the part that actually matters highlighted.
- ECT — Edge Crush Test
- Force in pounds per inch a one-inch strip of board withstands on edge before buckling. The best single predictor of stacking strength and the number to ask for on bulk containers.
- Mullen burst
- Pressure in psi required to rupture the board. Predicts puncture and rough-handling resistance. Historically the dominant spec, increasingly replaced by ECT.
- McKee formula
- The relationship used to estimate box compression strength from edge crush, board thickness and box perimeter. Why a taller box of the same board is weaker in a stack.
- Basis weight
- Weight of a liner or medium in pounds per thousand square feet. Higher generally means stiffer and stronger.
- Liner
- The flat facing sheets. Kraft liners use more virgin softwood fibre for strength; test liners use more recovered fibre.
- Medium
- The fluted inner layer. Usually lighter and higher in recycled content than the liners.
- Flute profile
- A, B, C, E and F, differing in height and count per foot. A gives the best vertical strength; B the best puncture resistance; C is the general-purpose compromise.
- Combined board
- The finished sandwich of liners and medium, glued and ready to convert.
- Caliper
- Total board thickness. A rough proxy for construction and the thing worth measuring when a stamp is illegible.
- Score
- A pressed crease the board folds along. Repeated folding here is one of the three genuine causes of wear.
- Butt joint
- A manufacturer's joint where two edges meet without overlap. Weaker than a glued lap joint and a common failure point on used stock.
- Delamination
- Liners separating from the medium. The box can look perfect and fail suddenly under load. Usually a reject.
Reuse performance
Which constructions survive being used again.
A general guide to how each construction holds up when used again. Heavier board generally survives more trips, which can make it the better value per trip despite a higher unit price.
| Construction | Reuse potential | Repairable? | Holds square? | Best reuse application |
|---|---|---|---|---|
| Single wall carton | Low | Rarely worth it | Poor once folded | One repeat packing cycle |
| Double wall carton | Low to moderate | Sometimes | Fair | Repeat shipping, kitting |
| Triple wall | Moderate | Yes | Good | Octabins, shallow trays |
| 4-wall bulk | Moderate to good | Yes, readily | Good | Internal handling, scrap collection |
| 5-wall bulk | Good | Yes, readily | Very good | Everything, including repeat outbound |
Send the load, not the wall count.
Weight, stack height, storage conditions and handling. A partner supplier follows up. Availability depends on partner suppliers.