The interior of a TARDIS is made up of a mix of exitonic circuitry and Block-Transfer mathematics. The Pedestrian infrastructure makes up the habitable interior of a TARDIS's internal quasi-dimensional continuum. As mentioned before, the total volume of rooms and corridors inside a TARDIS Micro-Universe has been described as being about the size of a small town. It is also known to be at least twice the size of San Francisco's China Town at the beginning of the 21st century. This means that a TARDIS's normal interior volume is between 13,000,000 and 60,000,000 cubic meters.

All rooms (aside from the 15 power rooms) are classified as Storerooms and make up the bulk of the pedestrian infrastructure. On average there is a room for every 3 meters of corridor or service tunnel. Thus there are between 180,000 and 710,000 rooms in a TARDIS (assuming standard configurations). The interior is organized by level, sector, tunnel, and room number. There are at least 12 levels which can be reached with stairs or lifts. The interior of a TARDIS is incapable of holding an object that is several miles across without extensive block-transfer modifications. Due to random dimensional feedback the interior layout of a TARDIS often changes slightly. This can also happen when a TARDIS diverts Artron Energy to assist in a Time Lord's regeneration.