ONS Data Structure

I have been looking through the ONS geographic data on their Geo Portal and there are acronyms and variables everywhere so I thought it best to understand what they all mean. Whenever I refer to the output areas and super output areas I’m referring to the ones as at the 2011 census in England and Wales.


Unique Delivery Point Reference. A unique eight-digit code representing each postal address in the Royal Mail PAF database


(I know what this is but for completion:) An alphanumeric value representing a number of addresses (UDPRNs) within an area. A full postcode known as the “Unit Postcode”

Postcodes are split into two parts, the inner and outer code, separated by a space.

The outer code is the bit before the space. The letter(s) at the start of the outer code is called the postcode area. See mapping postcodes in excel. The outer code is also known as the district.

The district and the numeric part of the inner code is called the sector.

Output Area (OA)

A cluster of adjacent postcodes with a minimum population (as at 2011 census) of 50 and 20 households. The aim was for them to contain 50 households.

Lower Layer Super Output Area (LSOA)

A cluster of adjacent output areas.

Middle Layer Super Output Area (MSOA)

A cluster of adjacent LSOAs

Population 1000-1200 5,000-15,000
Households 400-1200 2,000-6,000
Count 32,844 (England) 1909 (Wales) 6,791 (England) 410 (Wales)


Local Authority District (LAD)

The LSOAs and MSOAs line up with the 2011 local authority boundaries in England and Wales.


The highest level of area below country. Includes “South East”, “North West”, …etc.

The ONS Geoportal contains mappings between the above and more on top of that. The main postcode lookup file on the portal has all of these, plus may more, classifications for each postcode so you can merge this data on easily.

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