Because Choosing the Right Strength Spec Is the Difference Between a Protected Product and a Broken One
In corrugated paper distribution, the most common technical specs tossed around are ECT (Edge Crush Test) and BCT (Box Compression Test). They show up in RFPs, purchase orders, freight requirements, and packaging design briefs. But too often, these specs are chosen out of habit—not aligned with the real-world performance the client needs.
As a paper and packaging distributor, your job isn’t just to move material—it’s to recommend the right material for the application. That starts with understanding the difference between ECT and BCT, and applying best practices when specifying, validating, or advising on corrugated performance.
Let’s break it down.
What’s the Difference Between ECT and BCT?
TestWhat It MeasuresUse Case
ECT (Edge Crush Test)The force a corrugated board can withstand when compressed on its edge (lbs/in)Used to predict box stacking strength in vertical compression—especially for single-wall and double-wall board
BCT (Box Compression Test)The maximum force a fully assembled box can handle before failing under vertical loadProvides a more realistic simulation of stacked shipping boxes under warehouse or transit conditions
In short:
ECT is a material-level test.
BCT is a packaging-level performance indicator.
Why This Matters for Distributors
If you’re recommending or sourcing corrugated board for clients, your spec drives:
Pallet configuration
Freight safety
Storage planning
Supplier selection
Margin impact (heavier board = higher cost)
A box that fails under weight costs more than a damaged product—it costs trust, reorder confidence, and repeat business.
Best Practice #1: Understand the Relationship Between ECT and BCT
The McKee Formula is commonly used to estimate BCT based on ECT, board thickness, and box dimensions:
BCT ≈ 5.87 × ECT × √(board thickness × perimeter)
This gives a rough estimate of stacking strength—but assumes optimal construction and handling. In reality, palletization, humidity, and box design (RSC, FOL, die-cut) can shift BCT by 15–25%.
Never rely on ECT alone if the box will be stacked high or stored long-term.
Best Practice #2: Always Validate ECT Against Supplier Claims
Many mills and converters quote 32 ECT or 44 ECT as shorthand—but that’s only meaningful if the board was:
Tested under ASTM D6175 or TAPPI T811
Conditioned under ASTM D685
Verified at multiple points in the production run
Tip: Ask for the COA (Certificate of Analysis) with each shipment—or invest in your own ECT tester for incoming QA.
Best Practice #3: Don’t Over-Spec—Or Under-Spec
Over-specifying (e.g., using 44 ECT when 32 ECT suffices) drives up material costs and freight weight
Under-specifying leads to crush failures, transit damage, and rejected deliveries
Match specs to the actual environment:
Will boxes be double-stacked in a trailer?
Are they moving via parcel, pallet, or LTL?
Are they stored in a humid warehouse or dry climate?
Will they hold static loads or shifting contents?
The right ECT/BCT spec is not the strongest one—it’s the most appropriate one.
Best Practice #4: Use BCT to Validate Box Designs—Not Just Materials
If a customer is launching a new SKU, changing dimensions, or increasing case weight:
Run BCT testing on the actual box structure
Simulate real conditions: stretch wrap pressure, vertical stacking, and pallet configuration
This protects you (and the client) from assuming material strength = finished box performance.
Especially useful when supporting large-format boxes, die-cut windows, or custom folds.
Best Practice #5: Account for Environmental Conditions
Board strength decreases as humidity rises. In most cases:
ECT can drop up to 20% in high humidity
BCT failure is more likely after long dwell times in warm environments
Specify board that matches the climate of delivery, not just the origin.
For humid zones or high-moisture loads (produce, foodservice), consider wet-strength treated board or higher basis weight liners.
Best Practice #6: Customize Specs for High-Value or High-Risk SKUs
If your client is shipping:
Electronics
Heavy food cans
Medical kits
Subscription packs with fragile contents
…you may need both a higher ECT and custom box design with reinforcements.
Use BCT testing to validate not just whether the box holds—but how much margin of safety it offers.
Best Practice #7: Educate Your Clients on the Differences
Not all buyers understand that 32 ECT ≠ “good enough for everything.” Build trust by:
Offering spec consultations
Showing test results
Explaining tradeoffs between cost, performance, and handling requirements
A five-minute education upfront can prevent five truckloads of returns later.
ECT and BCT Are More Than Numbers—They’re Risk Management Tools
As a distributor, your value goes beyond quoting SKUs. You’re a partner in protecting product through the supply chain. That starts by knowing how to specify corrugated strength for real-world conditions—not just catalog sheets.
Choose specs that reflect the journey, not just the box. Test when the risk is high. And always link ECT to BCT when performance matters.
Because in this business, a box is only as good as the weight it can carry—and the trust it doesn’t crush.
