The sides of a container in nearly all cases, is corrugated. The depth of the corrugation is usually 1 inch (25mm), which means that 2 inches (50mm) is lost from the external width dimension (1 inch each side). The back (blank end) is also corrugated and the doors are around 2 inches (50mm) thick meaning that approximately 3 inches (75mm) is lost from the length.

The main reduction from external to internal dimensions is with height. The floor of a standard container has an underside clearance of approximately 6 inches (150mm) and the floor has a thickness of 27mm (1.1 inches). As the roof is corrugated another 1 inch (25mm) is lost resulting in an internal dimension of around 8 inches less than external – 7ft 10 inches (2.39m), though this can vary slightly either way depending on the floor thickness and construction method used.

Though the door height is additionally reduced because of the steel top rail above the door, this is a part of the structural integrity of the container, typically it’s 4 inches (100mm) thus reducing the entrance height to 7ft 6ins (2.28m), though this can vary slightly either way.