Many a times, people get confused between “Compression Strength” and “Stacking Load”.

Compression Strength (CS) is derived from Stacking Load (SL).

Stacking Load is the amount of physical load that a carton is expected to take during any point of its life-cycle.

Firstly check if the stack height of the warehouse is the same as the transportation.

If different, which one is higher? Use it for calculations.

The below sketch shows the calculation of a stack height of 10 cartons where each carton weighs 20 kg.

Stack load = (No. of Cartons in Stack – 1) x gross weight

= (10 – 1) x 20 kg (each carton)

= 9 x 20 kg

= 180 kg

We now know that 180 kg of stack load will come onto the lowest carton during warehousing or transpiration.

If Compression Strength of the carton was equal or less than the Stack Load, then the lowest carton would surely collapse.

Hence, Compression Strength = Stack Load x Safety factor (2 to 5)

Below is an approximate method of calculating your safety factor.

Q.1 : How far will the package travel from the factory?

Local | up to 500 km | 500 – 1000 km | 1000 – 2000 km | 2000 + km |

1 | 2 | 3 | 4 | 5 |

Q.2 : How long is the package supposed to be stored in a warehouse before it reaches the consumer?

1 Week |
1 – 4 Weeks |
1 – 3 Months |
3 – 6 Months |
6 – 12 Months |

1 |
2 |
3 |
4 |
5 |

Q.3 : Is the product fragile ? If the carton fails, is the products primary packaging designed (or capable) to take loads ?

e.g. Jam Bottles are glass and can take loads. Wafer pouches cannot take load. Tube lights are very fragile and cannot take loads.

Least Fragile |
Not Fragile |
Slightly Fragile |
Fragile |
Very Fragile |

1 |
2 |
3 |
4 |
5 |

Q.4 : Is the product expensive or hazardous?

Very Low |
Low |
Medium |
High |
Very High |

1 |
2 |
3 |
4 |
5 |

Q.5 : Is the product for export? or how big is your (or your customer’s) brand ?

Very Low |
Low |
Medium |
High |
Very High |

1 |
2 |
3 |
4 |
5 |

Now give marks to all 5 questions on a scale of 1 – 5, then calculate the average and round it off to the next higher digit. This is your safety factory for calculation of your Compression Strength specification.

**Disclaimer:** *The above is only a rough illustration of how to calculate the safety factor to find out the desired CS specification. The method and values shown above is not standard and may not be applicable to all types of products and package. The above information is generic only and may need some refinements or adjustments to suit your individual requirements.*