Shipping case minimum board strength requirements

Sizes/Materials

Below are a series of tables, they may be used - with caution - to calculate a likely pack board strength. In these tables products are assumed to be subjected to the most challenging shipping modality - parcel carrier. The following table provides guidelines for minimum recommended material strength for a range of slotted containers by dimension and weight. These simplified tables do not take into consideration perimeter vs. depth ratios and in no way relate to pack strength analysis such as the McKee Formula. These tables should only be used as a reality check in the absence of further analysis and testing, and only apply where none of the three dimensions exceed 7 times any other.

U.S. - Metric Converter

Material choice by size and weight - Imperial Units

Imperial Units L+W+D=<30" L+W+D=30" - 49.9" L+W+D=50" - 90"
< 10lbs 200T SW 275T SW 275T DW
10lbs - 19.9lbs 250T SW 275T SW 275T DW
20lbs - 29.9lbs 275T SW 275T DW 350T DW
30lbs - 39.9lbs 275T DW 350T DW 350T DW
40lbs - 65lbs 350T DW 350T DW 350T DW

Material choice by size and weight - Imperial Units - ECT

Imperial Units L+W+D=<30" L+W+D=30" - 49.9" L+W+D=50" - 90"
<10lbs 32 ECT SW 44 ECT SW 48 ECT DW
10lbs - 19.9lbs 40 ECT SW 44 ECT SW 48 ECT DW
20lbs - 29.9lbs 44 ECT SW 48 ECT DW 51 ECT DW
30lbs - 39.9lbs 48 ECT DW 51 ECT DW 51 ECT DW
40lbs - 65lbs 51 ECT DW 51 ECT DW 51 ECT DW

Material choice by size and weight - Metric Units - ECT

Metric Units L+W+D=<.75M L+W+D=.75M-1.19M L+W+D=1.2M - 2.3M
< 4.5kg 32 ECT SW 44 ECT SW 48 ECT DW
4.5kg - 8.9kg 32 ECT SW 44 ECT SW 48 ECT DW
9kg - 13.9kg 44 ECT SW 48 ECT DW 51 ECT DW
14kg - 17.9kg 48 ECT DW 51 ECT DW 51 ECT DW
18kg - 30kg 51 ECT DW 51 ECT DW 51 ECT DW

Material choice by Metric size and weight - Mullen Imperial Units

Metric Units

L+W+D=<.75M

L+W+D=.75M-1.19M

L+W+D=1.2M - 2.3M
><4.5kg >200T SW >275T SW >275T DW
>4.5kg - 8.9kg >250T SW >275T SW >275T DW
>9kg - 13.9kg >275T SW >275T DW >350T DW
>14kg - 17.9kg >275T DW >350T DW >350T DW
>18kg - 30kg >350T DW >350T DW >350T DW

Material choice by Metric size and weight - Metric Units ECT

Metric Units L+W+D=<.75M L+W+D=.75M-1.19M L+W+D=1.2M - 2.3M
<4.5kg 5.6 KN/m ECT SW 7.7 KN/m ECT SW 8.4 KN/m ECT DW
4.5kg - 8.9kg 5.6 KN/m ECT SW 7.7 KN/m ECT SW 8.4 KN/m ECT DW
9kg - 13.9kg 7.7 KN/m ECT SW 8.4 KN/m ECT DW 8.9 KN/m ECT DW
14kg - 17.9kg 8.4 KN/m ECT DW 8.9 KN/m ECT DW 8.9 KN/m ECT DW
18kg - 30kg 8.9 KN/m ECT DW 8.9 KN/m ECT DW 8.9 KN/m ECT DW

Material choice by Metric size and weight - Metric Units - Mullen

Metric Units L+W+D=<.75M L+W+D=.75M-1.19M L+W+D=1.2M - 2.3M
< 4.5kg 1380 KPa SW 1900 KPa SW 1900 KPa DW
4.5kg - 8.9kg 1725 KPa SW 1900 KPa SW 1900 KPa DW
9kg - 13.9kg 1900 KPa SW 1900 KPa DW 2415 KPa DW
14kg - 17.9kg 1900 KPa DW 2415 KPa DW 2415 KPa DW
18kg - 30kg 2415 KPa DW 2415 KPa DW 2415 KPa DW

Compression Strength - The BoxComp program can aid in calculating a required board grade for a unitized load with a great deal of accuracy. It should be remembered that the program is calibrated against state of the art corrugating and production machinery, as found in the better box plants around the world. Such machinery is not available to all manufacturers, however the customization features of BoxComp do enable some of the manufacture's deficiencies to be taken into account. Specifying board grades by the required performance characteristics is often the safest course of action. Paper qualities and make-up are also subject to variation by global region. Unitized load shipment, usually via either palletization or containerization normally means that board ECT would be the prime performance characteristic of any corrugated case. However, when using single item or mixed load shipping Burst strength should be given an equal degree of consideration. It should be noted that the performance of many die-cut designs are difficult to accurately predict without empirical data. This means that pack testing and transit trials are often necessary. See Compresive Forces in Packaging  and BoxComp Help for further information.

Safety factor is the primary variable that we can influence in establishing a relationship between McKee formula calculations and the various environmental factors to which a package will be exposed. A minimum safety factor of 3 is recommended in the absence of testing.

Economic Size Ratios for various styles of slotted container are provided for general guide to the most economic use of corrugated box material relative to the cubic volume contained, see HERE. These ratios do not take into consideration manufacturing efficiencies and user friendliness. The most economic use of corrugated for an RSC is a box whose depth is the same as the length and twice the width. Such high ratios of depth may not work well for multipacks where the products need to be easily unpacked or scanned in the box. They may, however work well for a mixed case situation. Pallet patterns are also a consideration in the determination of sizes and ratios.

Materials

ECT/Mullen Equivalents are guidelines to assist in selecting materials in the absence of ECT values. There is not a direct performance equivalence between ECT and Mullen. ECT values should provide the basis for selection whenever possible when compression strength is the objective.

Approximate Equivalence - ECT/Mullen

Single Wall ECT (lbs/in) Mullen (lbs/in2) Double Wall ECT (lbs/in)
32 200  
40 250  
44 275 48
55 350 51
  400 61
  500 71
  600 82

Approximate Equivalence - ECT/Mullen /Kpa/KN/m

Single Wall ECT (lbs/in)
PLI		 Single Wall ECT (KN/m) Mullen (lbs/in2) Burst (Kpa) Double Wall ECT (lbs/in)
PLI		 Double Wall
ECT (KN/m)
32 5.604 200 1379    
40 7.005 250 1724    
44 7.705 275 1896 48 8.406
55 9.632 350 2413 51 8.932
    400 2758 61 10.683
    500 3447 71 12.434
    600 4137 82 14.361