Corrugated Box Compression Test (BCT), McKee ECT Formula & Pallet Stacking Load Calculator
McKee Box Compression Strength (BCT) & Pallet Stacking Load Calculator
How This Box Crush (McKee ECT) & Stacking Calculator Works
Warehouse pallet failures occur when the bottom layer of corrugated shipping cartons (FEFCO 0201 RSC or 0427 mailers) buckles under the static weight of upper cartons combined with high relative humidity and long storage duration. Using the industry-standard Institute of Paper Chemistry (IPC) McKee Formula, our calculator determines the laboratory Box Compression Test (BCT) load from Edge Crush Test (ECT), flute caliper thickness (h), and box perimeter (2L + 2W), then applies environmental safety factors to output maximum safe working load (kg) and pallet stack height.
Governing Mathematical Equations (TAPPI T804 / ISO 12048 Box Compression & McKee ECT Structural Formula)
Relates vertical edge crush resistance (ECT), corrugated board thickness (h), and load-bearing perimeter Z = 2(L + W) to top-to-bottom carton crush load.
Divides lab crush strength by the environmental safety factor (SF = 3.0 for dry short-term transit up to SF = 5.5 for humid 90-day ocean freight).
Determines how many identical filled cartons can be stacked vertically in a column without crushing the bottom carton.
Standard Corrugated Flute Profiles, Calipers & ECT Ratings
| Flute Grade | Board Caliper (h) | Standard ECT Rating | Metric ECT (kN/m) | Primary Application |
|---|---|---|---|---|
| E-Flute (Micro Single-Wall) | 1.5 – 1.8 mm | 23 – 26 ECT | 4.0 – 4.5 kN/m | D2C e-commerce mailers (FEFCO 0427), retail displays |
| B-Flute (Standard Single-Wall) | 2.8 – 3.0 mm | 32 ECT | 5.6 kN/m | Canned goods, medium parcel cartons, die-cut trays |
| C-Flute (Shipping Single-Wall) | 3.8 – 4.0 mm | 32 – 44 ECT | 5.6 – 7.7 kN/m | Standard FEFCO 0201 RSC master shipping cartons |
| EB / BC Double-Wall | 4.5 – 6.8 mm | 48 – 61 ECT | 8.4 – 10.7 kN/m | Heavy industrial freight, export pallet boxes |
Apply These Calculations in 1:1 Parametric CAD Studios
FEFCO 0427 E-Commerce Mailer Box Dieline Generator
FEFCO 0201 Regular Slotted Container (RSC) Corrugated Shipping Box Dieline Generator
FEFCO 0422 Countertop PDQ Display Tray & Retail POS Merchandiser Dieline Generator
Frequently Asked Questions — Box Crush (McKee ECT) & Stacking
Why do boxes carry most of their load at the four vertical corners?
Over 65% of a corrugated carton's top-to-bottom compression resistance is concentrated within 50mm of the four vertical corner creases. That is why McKee's formula depends on perimeter Z = 2(L + W) rather than floor area.
What environmental safety factor (SF) should I select?
Use SF = 3.0 for dry indoor storage (<50% RH, under 10 days), SF = 4.0 for standard domestic distribution and pallet warehousing, and SF = 5.0 to 6.0 for high-humidity sea freight or interlocked pallet patterns.
How do I convert metric ECT (kN/m) to US Imperial ECT (lb/in)?
Multiply metric ECT in kN/m by 5.71015 to obtain lb/in (for example, 5.6 kN/m × 5.71 = 32.0 lb/in, which is standard 32 ECT board).