When looking at the strength of a container, one of the most important numbers to know is the payload of the container - being the max weight you can put in it. To calculate the payload (P) we just need to do some simple math.
First we look at the Maximum Gross Weight of the Container - or the max weight it can be (R). Then we subtract the container weight. The weight of an empty shipping container is the tare weight (T). This is simply the weight of container as it is, nothing in it. This gives us our P.
For our example, we'll use a 20' container with a max gross weight of 67,200 lbs and a tare weight of 4,830 lbs. This gives us a payload of 62,370 lbs.
Containers are really made to hold the weight through the corner posts and floor. While there is some strength in the walls or side panels of the container, they are not specifically designed to hold much weight.
End Panel Strength
The end panel of the container is tested to meet a uniform load minimum of 0.4 the payload, meaning 24,948 lbs. The key here is uniformly distributed across the entire end panel.
Side Wall Strength
The side wall is uniformly tested to hold 0.6 of the payload, or 37,422 lbs in our instance without buckling or breaking.