At the bottom of most shipping boxes there is a small, circular marking. Many consumers do not pay much attention to this marking, but this marking has the ability to answer an important question. Can the shipping box support what I am placing inside of it?
Typically referred to as a Box Makers Certificate, this marking provides information regarding the manufacturer of the shipping box and provides factual information relative to the tested strength of the shipping box. In addition to the manufacturer and testing strength, some markings include a maximum box size and a maximum gross weight (the total packaged weight) allowed.
One type of marking you may come across is ECT, Edge Crush Test. This test measures how much pressure the edges of the corrugated material can withstand before failing. This is important when stacking multiple boxes together because if the walls of the individual boxes fail under their own weight, then the entire stack falls apart.
For example, an average single-wall corrugate packaging carton will typically have a minimum ECT rating of 32. An ECT rating of 32 is not an indication of how much weight your product weighs individually. Instead, it represents a strength test for the thickness of the corrugated board. Therefore, you need to carefully read through the entire marking as both the box size, total load, design and transportation route can impact whether you are selecting the correct carton for the task.
In some cases, a packaging supplier may provide a Burst Rating instead of an ECT Rating. A Burst Rating tests how much pressure a particular section of the corrugated board can withstand until it ruptures. Because Burst Ratings and ECT ratings are measuring two completely separate aspects of a carton's performance, neither is interchangeable with the other.
Prior to purchasing shipping containers begin by determining the overall weight of the product along with any additional products used such as packing materials (paper/pads), inner wrapping and tape. For example, an eight-pound product may increase in weight to eleven pounds once all additional items are added. Next, compare that total weight against the gross weight indicated on the certificate and always ship below that value.
You also need to give consideration to the size restrictions listed on the certificate. Typically, these restrictions reference the total dimensions of the box including the height and are based upon the strength characteristics of the specific carton. The size requirements for shipping contained within a carrier's pricing structure is not related to these certification values.
A certification only guarantees that the carton was in good condition prior to shipping. If damage occurred during transit (i.e., water exposure, crushing of corners, cutting etc.), then the actual performance characteristics of the container will likely degrade. Moreover, a damaged carton may have reduced strength compared to a brand-new carton even though it has been rated equally.
If you purchase pre-made shipping containers, create a listing of expected pack weights and box sizes prior to ordering. When speaking with your sales representative share your expectations and request guidance on which rating will meet your needs. Although there are no absolute guarantees regarding your carton selection, expensive and/or large shipments or fragile goods may require sending a few packages to determine potential issues prior to making mass shipments.











