Box Strength & Burst Ratings (ECT vs Mullen)

Direct Answer

Corrugated cardboard shipping boxes are legally rated under two distinct testing standards stamped inside the Box Maker's Certificate (BMC): the Edge Crush Test (ECT, measuring top-to-bottom compression stacking strength in lbs/in) and the Mullen Bursting Test (measuring puncture resistance and rough handling in lbs/sq in).

Source: ASTM D2808 / TAPPI T 811 (ECT) / TAPPI T 810 (Bursting Strength) / Item 222 NMFC Rules · Last reviewed Aug 28, 2026

Specs

Governing Standards	TAPPI T 811 / TAPPI T 810 / ASTM D2808 / NMFC Item 222 (National Motor Freight)
Edge Crush Test (ECT)	Measures compressive edgewise strength (lbs/linear inch) parallel to fluting — predicts pallet stacking capacity
Mullen Bursting Strength	Measures hydraulic pressure (psi / lbs per sq inch) required to rupture the linerboard face — predicts puncture survival
Standard Single-Wall 32 ECT	Equivalent to 200# Burst \| Max Gross Weight: 65 lbs (29.5 kg) \| Max Total Dimensions (L+W+D): 75 inches (190 cm)
Heavy-Duty 44 ECT	Equivalent to 275# Burst \| Max Gross Weight: 95 lbs (43.1 kg) \| Max Total Dimensions: 95 inches (241 cm)
Double-Wall 48 ECT	Equivalent to 275# Double-Wall \| Max Gross Weight: 100 lbs (45.4 kg) \| Max Dimensions: 100 inches (254 cm)
Double-Wall 51 ECT	Equivalent to 350# Double-Wall \| Max Gross Weight: 120 lbs (54.4 kg) \| Max Dimensions: 105 inches (267 cm)

Corrugated Box Maker's Certificate (BMC) Rating Conversion Table

Corrugated Wall Type	Edge Crush Test (ECT Rating)	Mullen Burst Test Rating	Maximum Recommended Gross Weight (lbs)	Maximum Outside Dimensions (L+W+D)
Single-Wall	23 ECT	125# Mullen	20 lbs (9 kg)	40 inches (102 cm)
Single-Wall	26 ECT	150# Mullen	35 lbs (16 kg)	50 inches (127 cm)
Single-Wall (Standard)	32 ECT	200# Mullen	65 lbs (30 kg)	75 inches (190 cm)
Single-Wall (Heavy)	44 ECT	275# Mullen	95 lbs (43 kg)	95 inches (241 cm)
Single-Wall (X-Heavy)	55 ECT	350# Mullen	120 lbs (54 kg)	105 inches (267 cm)
Double-Wall (Heavy)	48 ECT	275# Mullen	100 lbs (45 kg)	100 inches (254 cm)
Double-Wall (X-Heavy)	51 ECT	350# Mullen	120 lbs (54 kg)	105 inches (267 cm)
Triple-Wall (Industrial)	80+ ECT	700# to 1100#	240+ lbs (109 kg)	120 inches (305 cm)

Why Modern Logistics Switched from Mullen Burst to ECT

Historical Mullen Test (Puncture Focus): Developed when packages were tossed manually between railcars, favoring heavy, virgin Kraft fibers to resist punctures.
Modern ECT (Pallet Stacking Focus): Modern automated logistics stacks pallets 3-high inside warehouses. The Edge Crush Test directly calculates warehouse pallet racking compression limits using McKee's Formula, allowing manufacturers to use lightweight recycled fibers without sacrificing vertical stacking integrity.