Packaging Mechanics, Warehousing & Supply-Chain Ops
McKee Corrugated Box Compression (BCT) & Stacking Formula
Calculate R.C. McKee’s Simplified Corrugated Box Compression Strength BCT_lbf = 5.87 * ECT_lb_in * SQRT(Flute_Caliper_in * Box_Perimeter_in), Humidity/Creep Safe Bottom-Box Load, and Maximum Safe Pallet Layers.
Derate laboratory McKee BCT for warehouse humidity and creep before stacking pallets!
When palletized Regular Slotted Containers (RSCs) collapse in humid ocean containers or 90-day DC racks, the root cause is usually confusing dry laboratory Peak Box Compression Test (BCT) strength with long-term warehouse safe load! R.C. McKee, Gander, and Wachuta (1963, Paperboard Packaging) proved that vertical panel buckling concentrates load in the four vertical box corners, yielding the industry-standard Simplified McKee Equation: Lab_BCT_lbf = 5.87 * ECT_lb_in * SQRT(Flute_Caliper_in * Perimeter_in), where ECT is Edge Crush Test strength (lb/in) and Perimeter_in = 2 * (Length_in + Width_in)! Multiplying Lab_BCT by a combined Humidity/Creep/Interlock Knockdown Factor F_env (typically 0.20–0.25 for 80% RH long-term storage) gives Safe Bottom-Carton Load, supporting 1 + INT(Safe_Load / Carton_Weight) total stacked layers (since the bottom carton supports only the N - 1 cartons ABOVE it)!
Verify on a 32-ECT C-Flute Carton—Board_ECT = 32 lb/in (B2), C_Flute_Caliper h = 0.16 in (B3), Carton_Length = 20 in (B4), Carton_Width = 12 in (B5 -> Perimeter Z = 2 * 32 = 64 in in E2, with SQRT(0.16 * 64) = 3.20 exact!), Environmental_Safety_Factor F_env = 0.25 (B6), and Gross_Carton_Weight = 30 lb (B7): Dry Lab McKee BCT is 5.87 * 32 * 3.2 = 601.09 lbf (E3); Safe Long-Term Bottom Load is 601.09 * 0.25 = 150.27 lbf (E4); allowing 1 + INT(150.27 / 30) = 6 total stacked layers (5 upper cartons = 150 lb on the bottom carton, E5)!
| McKee Corrugated Metric (32 ECT, 0.16" C-Flute, 20x12" RSC, F_env=0.25, 30 lb/box) | Formula | Verified Output |
|---|---|---|
| Carton Perimeter Z (inches) | 2 * (Length_in + Width_in) | 64.00 in |
| Dry Lab McKee Strength BCT (lbf) | 5.87 * ECT * SQRT(Caliper * Z) | 601.09 lbf (751.36 lbf @ 40 ECT) |
| Safe Warehouse Bottom Load (lbf) | Lab_BCT * F_env | 150.27 lbf (187.84 lbf @ 40 ECT) |
| Max Safe Pallet Layers High | 1 + INT(Safe_Bottom_Load / Box_lb) | 6 Layers (7 Layers @ 40 ECT) |
Simplified McKee Box Compression Test (BCT) Formula
Validate ECT > 0, Flute_Caliper > 0, Length & Width > 0, environmental factor 0 < F_env <= 1, and Carton_Weight > 0!
=LET(ec_t, B2, fl_h, B3, ln_b, B4, wd_b, B5, sf_f, B6, bx_w, B7, IF(OR(ec_t <= 0, fl_h <= 0, ln_b <= 0, wd_b <= 0, sf_f <= 0, sf_f > 1, bx_w <= 0), "Invalid Corrugated Box Spec", LET(pr_z, 2 * (ln_b + wd_b), ROUND(5.87 * ec_t * SQRT(fl_h * pr_z), 2))))40-ECT Heavy-Duty Board Upgrade Check
Upgrade Board_ECT B2 from 32 to 40 lb/in: Lab BCT rises to 751.36 lbf, Safe Load reaches 187.84 lbf, and Max Safe Stack Height increases to 7 total layers!
=IF(ISTEXT(E3), E3, 1 + INT(E4 / B7))Try the example
Use the original values or change them to test your understanding.