The TEU is a 20’ long container. Average size container we see today is 40’ long, but the TEU is the standard measurement. You can imagine how fast the loading and unloading occurs. Roughly speaking, a modern port can load a container ship with no unplanned delays at a rate of up to 100 containers per hour. Of course, a vessel doesn’t load and unload entirely at any single port at it may visit a number of ports loading and unloading both full and empty boxes. An amazing “dance” at any port.

A gantry crane unloads containers from a cargo ship at the Long Beach Container Terminal at the Port of Long Beach in Long Beach, California, U.S., on Wednesday, April 4, 2018.
Photographer: Tim Rue/Bloomberg