The corridor width of a building is the median distance between the facing surfaces of the two bounding walls of the main passageway for foot traffic in a building. It should be measured perpendicular to the walls, and does not include the wall thickness. The main corridor may run through the center of the building, along its side, or wind through the floorplan with several turns. It does not necessarily have to be straight.

This measurement applies primarily to large buildings with multiple units or divisible interior spaces. However it can be applied to smaller buildings when a clearly defined corridor is present.

The median describes the middle of the measured corridor-width values. A local widening or narrow point does not automatically supply the value, and a turn in the route does not add wall thickness to the width.