CM1 postcode district: Chelmsford and around, Essex

CM1 is a postcode district in Essex, with 1,561 postcodes in use in 7 sectors. It has postcodes in Chelmsford, Writtle, Broomfield and 1 more place. It is split between 2 councils: Chelmsford (1,535 postcodes) and Uttlesford (26).

Postcodes in use: 1,561
Sectors: 7
Councils: 2 councils
Places: 4 places

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

Every postcode in CM1, and which are new since 2020

New since 2020: 133
In use before 2020: 1,428
Outline: where 5 or more new postcodes since 2020 lie together

Of the 1,561 postcodes in CM1 that ONS places, 133 are new since 2020 and 1,428 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 160 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 51.7475, longitude 0.4583. 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

CM1 7GHJuly 2026 CM1 9FXJuly 2026 CM1 9JEJuly 2026 CM1 9QFJuly 2026 CM1 9RPJuly 2026

Where the new postcodes lie together

36 new postcodes since 2020, outlined on the map. CM1 9FX, is the newest of them.
24 new postcodes since 2020, outlined on the map. CM1 6HQ, is the newest of them.
20 new postcodes since 2020, outlined on the map. CM1 6PE, is the newest of them.
8 new postcodes since 2020, outlined on the map. CM1 4FZ, is the newest of them.
5 new postcodes since 2020, outlined on the map. CM1 1UQ, is the newest of them.

What broadband can you get in CM1?

Ofcom reports on 1,449 of the 1,561 postcodes in CM1. At 1,195 of them every home and business can get gigabit broadband, and at 4 some cannot get decent broadband (10 Mbit/s).

Postcodes where every home can get gigabit1,195 of 1,449

Postcodes where every home can get superfast1,373 of 1,449

Postcodes where some cannot get decent broadband4 of 1,449

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 CM1 at risk of flooding?

86 of the 1,561 postcodes in CM1 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 314 homes and businesses in an area at high or medium risk.

Homes and businesses in an area at risk, at 86 of 1,561 postcodes High: 64Medium: 250Low: 662Very low: 101

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 CM1?

Homes in CM1 sold for a typical £395,000 in the 12 months to August 2026, across 739 sales, down 2.5% on the 12 months before, HM Land Registry's figures show.

£395,000 typical price, the 12 months to August 2026

£405,000 12 months to August 2025

▼ down 2.5% on the 12 months before

Detached £605,000 168 sales
Semi-detached £432,500 237 sales
Terraced £367,500 158 sales
Flat or maisonette £220,500 176 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