The area covered is of high density development, and includes parts of the City of Westminster and the London Boroughs of Camden and Islington, plus a very small part of the City of London.

When the districts are used for purposes other than the sorting of mail, such as for geographic reference and on street signs, their subdivisions - featuring letter suffixes - are often omitted.

Deliveries for the area come from Mount Pleasant Mail Centre, west of Farringdon Road.

The postcode districts are, with approximate coverage: The WC1 postcode district (51°30′50″N 0°07′12″W / 51.514°N 0.120°W / 51.514; -0.120 (WC1)) is roughly bounded by Amwell Street, Rosebery Avenue and Gray's Inn Road to the east; New Oxford Street and High Holborn to the south (the boundary with WC2); Tottenham Court Road to the west; and Euston Road and Pentonville Road to the north, and approximately corresponds to the modern district of Bloomsbury, with parts of Holborn, King's Cross and St Pancras.

It includes the British Museum and buildings owned by the federal University of London and its constituent colleges and institutes.