Archived from http://www.geog.leeds.ac.uk/people/o.duke-williams/smstab/opcs_codes.html - as the original is no longer available.
The majority of Census statistics are reported for a set of small areas. All these areas have identification codes devised by the Office for Population Censuses and Surveys (OPCS) and the General Register Office (GRO), Scotland.
The OPCS is now combined with the Central Statistical Office, and known as the Office for National Statistics (ONS), although the identification labels are still generally referred to as 'OPCS codes'.
There are a few conceptual differences between the structure of the codes (or rather, the underlying geography) as used in England and Wales, and as used in Scotland. The description below outlines the way codes are structured in England and Wales, and notes about the differences in Scotland are added at the end.
The codes are designed to be hierarchical: as the level of detail becomes finer, the label is extended by adding another element. For example, the OPCS code for the district Leeds is 08DA. This label incorporates the highest two levels of the geographical hierarchy commonly used in administrative geography; the first two characters - 08 - are the county number, while the next two letters - DA - are a district code. District codes are unique for each district, and thus the county code is sometimes omitted from the label.
There are two further levels that can be referred to with OPCS labels, wards and enumeration districts (EDs). Wards are referred to using a further two letters. The code for the ward 'University' in Leeds is 'GF'. The ward element of the code is not unique - the total number of possible two letter pairs is much smaller than the total number of wards, and in practice only a very limited number are used. Thus, to refer to the University ward in Leeds, the full code should be given: 08DAGF. Each ward is split up into a number of enumeration districts - one for each census enumerator - and these are given two digit codes. These are generally, but not always, numbered in sequence. For example: the University ward in Leeds consists of 47 enumeration districts, but these are numbered from 01 to 58, obviously with some gaps in the sequence. As with wards, to refer to a specific ED, the whole code must be given, e.g.: 08DAGF01.
The way in which codes are constructed for areas in Scotland are broadly similar, but there are some important conceptual differences. Whereas the hierarchy of areas in England and Wales consists of counties, districts, wards and EDs, in Scotland that hierarchy consists of regions, districts, postal areas and output areas. Districts are divided up using 'building blocks' based on postal geography. Usually these are postal sectors, but where postal sectors are large or straddle district boundaries, they may be split into part-postal sectors. Output areas are the smallest level of geography used in Scotland.
The OPCS codes used in Scotland have the same format as those used elsewhere, with the important exceptions that districts are referred to with a pair of digits rather than a pair of letters, and that output area codes can have a trailing letter after the usual two digits. For example, the district Edinburgh City for the code 6229, which includes the county code 62 for Lothian, and a separate district code. As in England and Wales, the district code in unique, and thus the county code is sometimes omitted. Within this district, two letter codes are used (as with wards in England and Wales) to refer to postal sectors. These letter pairs do not have any relationship to the letters used in the postcode; for example the code for the postal sector EH1 1 (which should include Edinburgh's central Post Office) is 6229AA. This area contains only one output area, 6229AA01, although the sector EH1 2 contains two output areas, 6229AA02A and 6229AA02B.
The OPCS codes for all areas can be found at MIDAS on the gopher information server, via the menus:
The URL for this is:
The gopher server is accessible via the MIDAS web server; Census information can be found at: