The standard external width of an intermodal shipping container is 8 feet.
The 8-foot width is one of the key dimensions that lets containers move between ships, trains, and trucks without repacking their cargo. The International Organization for Standardization established widely used container standards through the ISO 668 series, which covers dimensions, ratings, and handling requirements.
A common dry container is 8 feet wide and 8 feet 6 inches high, with the most familiar lengths being 20 feet and 40 feet. The 20-foot container provides the “TEU,” or twenty-foot equivalent unit, used to measure ship and terminal capacity. A 40-foot container counts as two TEUs.
The width can seem confusing because some specialized containers are slightly wider, and “high-cube” containers are taller rather than wider. The listed alternatives—9.5 feet, 40 feet, and 20 feet—refer to neither the standard external width nor, in the latter cases, the usual container length distinction.