SO21 postcode district: Colden Common and around, Hampshire

SO21 is a postcode district in Hampshire, with 743 postcodes in use in 3 sectors. It has postcodes in Colden Common, Twyford, Winchester, Eastleigh and 2 more places. It is split between 4 councils: Winchester (692 postcodes), Test Valley (43), Basingstoke and Deane (7) and 1 other.

Postcodes in use: 743
Sectors: 3
Councils: 4 councils
Places: 5 places

Source: Office for National Statistics (ONS) Postcode Directory, August 2026, loaded 20 October 2026. See all our data sources

Every postcode in SO21, and which are new since 2020

New since 2020: 20
In use before 2020: 723
Outline: where 5 or more new postcodes since 2020 lie together

Of the 743 postcodes in SO21 that ONS places, 20 are new since 2020 and 723 were in use before 2020.

Each mark is a postcode's centre point as ONS gives it, not a building. Press one to see its postcode and open its page. New since 2020 means it came into use in January 2020 or later. A dashed outline shows where 5 or more lie within 240 metres of each other. It is not a boundary, and no boundary is drawn. Where marks overlap, the one first in the key is drawn; the counts include every postcode.

The middle of its postcodes: latitude 51.0752, longitude -1.3166. Open this area on OpenStreetMap

Source: Office for National Statistics (ONS) Postcode Directory, August 2026, loaded 20 October 2026, the centre point of each postcode; when each came into use: the same directory; roads, rivers and built-up areas: Contains OS data © Crown copyright and database right 2026. Drawn by us. Street map: Ordnance Survey, OS Open Zoomstack, Open Government Licence v3.0, drawn with MapLibre. How we use them

The 5 newest postcodes

SO21 3FYJuly 2025 SO21 2FUMarch 2025 SO21 2FRSeptember 2024 SO21 3GAAugust 2024 SO21 1GPJune 2024

Where the new postcodes lie together

6 new postcodes since 2020, outlined on the map. SO21 1GD, is the newest of them.

What broadband can you get in SO21?

Ofcom reports on 734 of the 743 postcodes in SO21. At 178 of them every home and business can get gigabit broadband, and at 15 some cannot get decent broadband (10 Mbit/s).

Postcodes where every home can get gigabit178 of 734

Postcodes where every home can get superfast523 of 734

Postcodes where some cannot get decent broadband15 of 734

Ofcom gives each postcode's share of homes and businesses, not how many there are, so these count postcodes. Each postcode page has its own figures. A provider's checker answers for one address.

Check one address on Ofcom's checker

Source: Ofcom, Connected Nations, Spring 2026, data for January 2026, Open Government Licence v3.0. How we use it

Is SO21 at risk of flooding?

48 of the 743 postcodes in SO21 have a home or business in an area at risk of flooding from rivers or the sea, the Environment Agency says. At those, it puts 77 homes and businesses in an area at high or medium risk.

Homes and businesses in an area at risk, at 48 of 743 postcodes High: 50Medium: 27Low: 64Very low: 65

High: 3.3% or more a year (1 in 30). Medium: 1% to 3.3% a year. Low: 0.1% to 1% a year. Very low: under 0.1% a year (1 in 1,000). Each band is the chance of flooding in any one year.

Homes and businesses in an area at risk of flooding from rivers or the sea, as the Environment Agency counts them, added up over the postcodes. It is for the land, not each building, and leaves out surface water, groundwater and sewers. Each postcode page has its own figures and its flood warning areas.

Source: Environment Agency, Risk of Flooding from Rivers and Sea (postcodes in areas at risk), published 6 July 2026, Open Government Licence v3.0. How we use it

What do homes sell for in SO21?

Homes in SO21 sold for a typical £529,000 in the 12 months to August 2026, across 190 sales, down 11.8% on the 12 months before, HM Land Registry's figures show.

£529,000 typical price, the 12 months to August 2026

£600,000 12 months to August 2025

▼ down 11.8% on the 12 months before

Detached £773,000 83 sales
Semi-detached £445,000 56 sales
Terraced £398,750 38 sales
Flat or maisonette £233,000 13 sales

Each bar is that kind's typical price, against the most expensive kind here.

Standard sales of homes at market value. A typical price is the median, the middle sale. Sales take weeks to be registered, so the last month or two are incomplete. Each postcode page gives the figure for its own postcode sector.

Source: HM Land Registry Price Paid Data, files dated 28 September 2026. Contains HM Land Registry data © Crown copyright and database right 2021. This data is licensed under the Open Government Licence v3.0. How we use it