No question about it: the key figure in connection with ocean freight containers is 20. After all, transshipment of these boxes in ports from Los Angeles to Laem Chabang is measured in TEU, in Twenty-foot Equivalent Units. And yet: according to the ISO standard, the boxes actually only measure 19 feet 10.5 inches. Or, expressed in the metric system: instead of 6.096 meters, they only measure 6.058 meters. Yet the 40-foot containers that are just as common in global ocean freight really do measure 40 feet. Why is that?
The slight discrepancy ensures that on board ships, one 40-foot container can safely be placed on top of two 20-foot containers, and vice versa. Because, in addition to the container lengths, the positions of the twist locks used to secure the boxes are also defined precisely. The result is that there will always be a certain space between two 20-foot variants; the boxes therefore need to be just a touch shorter than their name would suggest.
40’s 40 yet 20 isn’t 20: With regard to the lengths of ocean freight containers, special rules apply. Photo: iStock/baona