How many boxes fit in a 20 foot container calculator

Use this calculator to easily calculate how many items with particular dimensions you can fit in a container. Container stacking calculator.

    Quick navigation:

1. Using the container calculator
2. List of standard container types
3. Container loading: internal stacking calculation
4. Container utilization vs. ease of internal stacking

    Using the container calculator

This is a fairly simple container loading calculator: it allows you to calculate how many items of the same dimensions and weight (optional) you can fit in a single shipping container. Currently it only supports simple stacking, meaning that each item will be placed next to the other, no complex rotations or ordering. While complex ordering can, in some cases, lead to stacking slightly more items, it is also more difficult for the people filling the containers to follow precisely.

For your convenience we have entered 8 of the most widely used container sizes in international shipping, so that you can perform the calculations quicker. For each of them we also have an estimate of the maximum load, so if you were to enter the weight of the item we will also calculate the overall cargo weight and warn you if it goes over the maximum container weight capacity. See below for a list of the standard sizes & maximum cargo weight.

    List of standard container types

The table represents the dimensions of the 8 standard container types that are predefined in our calculator. The internal dimensions are slightly different than the minimum internal size in ISO 668:2013, since in practice most manufacturers will deliver containers with larger internal dimensions (higher capacity, larger internal volume) than the minimum specs. The maximum payload is calculated based off the ISO standard, subtracting common tare weights.

Since each manufacturer produces slightly different containers, if you know the exact dimensions and maximum load capacity, then it is best to specify them using our container calculator's "Custom" option.

    Container loading: internal stacking calculation

In order to estimate how many items you can fit, you need to determine the optimal way to stack them so that you minimize unused volume in the container. This is a hard problem to solve, a so-called NP-hard problem (NP-problem stands for "Non-deterministic Polynomial acceptable problems"), meaning that they cannot be solved in polynomial time.

However, if we limit ourselves to simple orderings of the items, in which all items are oriented the same way with respect to the container interior, then there are only six ways you can arrange a set of items with 3 dimensions (the cargo) in a 3-dimensional box (the container). You can use our Combinations calculator to check that if unsure - 3 objects, choose 2 from each. If we denote the width, height and length of each item with w, h and l, and the corresponding container dimensions with W, H, and L, then these look like so:

• Orient w alongside W, h alongside L, l alongside H
• Orient w alongside W, l alongside L, h alongside H
• Orient h alongside W, w alongside L, l alongside H
• Orient h alongside W, l alongside L, w alongside H
• Orient l alongside W, w alongside L, h alongside H
• Orient l alongside W, h alongside L, w alongside H

Once you know the alignment, you can calculate for each of the six stacking orders how many items you can fit in the volume, by iteratively adding items in each container dimensions until you run out of space in that direction. Then you can compare the total used volume (or number of items, if the items are the same) in each of the six cases and select the variant that makes best use of the available space. Or, instead of going through all this hard work you can let our container calculator do the job for you.

    Container utilization vs. ease of internal stacking

In order to understand the issue it is useful to do a brief review of the fascinating history of the shipping container [2], which we owe to the invention of Malcolm McLean. Upon noticing that a significant part of the cargo transportation time and costs are associated with port costs (some analysis from the late 1950s say 60-70%, others find lower numbers at ~40% of total costs), McLean invented the shipping container to reduce shipping time and costs. It should be noted that the costs were not only direct ones, but also loses due to cargo damaged during handling, loading and unloading. The first containers of the McLean company started travelling on April 26, 1956. Loading costs have since plummeted from $5.86 to about $0.16 per ton (97% reduction)! Loading times have improved from 1.3 tonnes per hour in 1965 to 30 tonnes per hour in 1970, to over 74 tonnes per hour by 1980. In the mid-1980s some Asian ports where loading 24 containers per hour [3]! (each of which may be loaded to a different extent, but 28 tonnes per container is possible)

Before that you had cases, cartons, bags, boxes, bundles, drums, cans, barrels, crates, reels, etc. You needed to waste an inordinate amount of time manually handling all of these small, differently sized and weighted items. Now that you have a container, you no longer need to do that, but if you want maximum utilization, this might mean increasing the amount of manual work and its complexity (and thus execution time). While for port and ship operators it is all about how many tonnes they can shift per hour, for the people handling the contents of the containers the simplicity of the internal stacking can make a significant difference, so consult them if considering a more complex scheme that will utilize a slightly higher percentage of the volume.

In the end you want to take the advantage of containerization which is that as long as the items are in the container, they travel very cheap and relatively fast, without going overboard while trying to stuff as many items as theoretically possible.

    References

[1] ISO 668:2013

[2] Tomlinson J. (2009) "History and Impact of the Intermodal Shipping Container", Pratt Institute

[3] Trace K. (1988) "Handmaiden of Trade: A Study on ASEAN-Australia Shipping", Singapore University Press p.127

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