CB postcode district map, Cambridge
Supplier statuses last checked .
The CB postcode area covers 16 districts and 11,252 live postcodes, from CB1 to CB25. It is centred on Cambridge and also covers Ely, Haverhill, Saffron Walden, Newmarket and Soham.
Districts here average 703 postcodes.
Where the CB districts sit
3 districts are plotted without a label where labels would overlap; every one is in the table below.
Where CB sits
It falls across Cambridgeshire, Essex and Suffolk.
Water supply across CB
All 16 CB districts are supplied by Cambridge Water. That makes CB simple in a way many areas are not: one company, one set of rules, one status to check.
Cambridge Water has a hosepipe ban in force from 17 July 2026, covering the whole of CB.
The shape of the CB area
CB1 is the largest district with 1,159 postcodes around Cambridge, and CB5 the smallest with 279. The area divides into 69 postcode sectors.
The numbering is not continuous. CB runs up to 25 but has only 16 districts, so 9 numbers are unused:.
Several districts share a settlement, which is a common source of confusion when a form rejects an address: CB1, CB2, CB3, CB4, CB5, CB22, CB23 and CB24 all point at Cambridge, CB6 and CB7 all point at Ely and CB9 and CB21 all point at Haverhill.
What borders CB
CB sits next to SG (Stevenage) to the south west, CM (Chelmsford) to the south, PE (Peterborough) to the north, AL (St Albans) to the south west and EN (Waltham Cross) to the south.
CB districts, settlements and water supply
| District | Principal settlement | Water company | Hosepipe ban status |
|---|---|---|---|
| CB1 | Cambridge | Cambridge Water / Anglian Water | Ban in force |
| CB2 | Cambridge | Cambridge Water / Anglian Water | Ban in force |
| CB3 | Cambridge | Cambridge Water / Anglian Water | Ban in force |
| CB4 | Cambridge | Cambridge Water / Anglian Water | Ban in force |
| CB5 | Cambridge | Cambridge Water / Anglian Water | Ban in force |
| CB6 | Ely | Cambridge Water / Anglian Water | Ban in force |
| CB7 | Ely | Cambridge Water / Anglian Water | Ban in force |
| CB8 | Newmarket | Cambridge Water / Anglian Water | Ban in force |
| CB9 | Haverhill | Cambridge Water / Anglian Water | Ban in force |
| CB10 | Saffron Walden | Cambridge Water / Anglian Water | Ban in force |
| CB11 | Saffron Walden | Cambridge Water / Anglian Water | Ban in force |
| CB21 | Haverhill | Cambridge Water / Anglian Water | Ban in force |
| CB22 | Cambridge | Cambridge Water / Anglian Water | Ban in force |
| CB23 | Cambridge | Cambridge Water / Anglian Water | Ban in force |
| CB24 | Cambridge | Cambridge Water / Anglian Water | Ban in force |
| CB25 | Soham | Cambridge Water / Anglian Water | Ban in force |
Principal settlement is the town or city each district sits in or nearest to, derived from OS Open Names. It is not the Royal Mail post town, which is licensed data and not published openly. Status is resolved live from each company’s own notice.
Water hardness in CB
No water company covering CB publishes hardness figures as open data. The gap is named per district below so you know who to ask.
| District | Hardness | As published | Supply zone | Published by |
|---|---|---|---|---|
| CB1 | Not published by Cambridge Water. Check with your supplier. | |||
| CB2 | Not published by Cambridge Water. Check with your supplier. | |||
| CB3 | Not published by Cambridge Water. Check with your supplier. | |||
| CB4 | Not published by Cambridge Water. Check with your supplier. | |||
| CB5 | Not published by Cambridge Water. Check with your supplier. | |||
| CB6 | Not published by Cambridge Water. Check with your supplier. | |||
| CB7 | Not published by Cambridge Water. Check with your supplier. | |||
| CB8 | Not published by Cambridge Water. Check with your supplier. | |||
| CB9 | Not published by Cambridge Water. Check with your supplier. | |||
| CB10 | Not published by Cambridge Water. Check with your supplier. | |||
| CB11 | Not published by Cambridge Water. Check with your supplier. | |||
| CB21 | Not published by Cambridge Water. Check with your supplier. | |||
| CB22 | Not published by Cambridge Water. Check with your supplier. | |||
| CB23 | Not published by Cambridge Water. Check with your supplier. | |||
| CB24 | Not published by Cambridge Water. Check with your supplier. | |||
| CB25 | Not published by Cambridge Water. Check with your supplier. | |||
Hardness is published per census area, not per postcode, so these figures characterise a district rather than measuring one address. They are a scale and taste matter, not a safety one. Hardness data version wessex-water@2022-2025+yorkshire-water@2026.
Download the CB data
No signup, no email wall. GeoJSON carries the district points, the supplier and the live status, so it can be dropped straight into a map.
District positions are averaged postcode centroids from OS Code-Point Open. They show roughly where a district sits, not where its boundary runs, and are not legal boundaries.
Frequently asked questions
How many postcode districts are in the CB area?
There are 16 CB postcode districts, running from CB1 to CB25, and they contain 11,252 live postcodes across 69 sectors.
What towns does the CB postcode area cover?
CB covers Cambridge, Ely, Haverhill, Saffron Walden, Newmarket and Soham. The area takes its name from Cambridge, and each district is listed with its settlement in the table on this page.
Which water company supplies CB postcodes?
Cambridge Water supplies all 16 CB districts. Supply boundaries follow the pipe network rather than postcode geography, so confirm against your water bill if you are near the edge of the area.
Why do CB1 and CB2 both say Cambridge?
CB1, CB2, CB3, CB4, CB5, CB22, CB23 and CB24 all serve Cambridge, covering different parts of it. A single town routinely needs more than one postcode district once it passes a few thousand delivery points, so this is normal rather than an error in an address.
Can I download a free CB postcode map?
Yes. This page offers the CB districts as GeoJSON, CSV and SVG, free and with no signup or email address required. The GeoJSON carries each district's position, its water company and its current restriction status, so it can be dropped straight into a mapping tool.
Which councils cover the CB postcode area?
CB reaches into Cambridgeshire, Essex and Suffolk. A postcode area is not a council area: they were drawn for different purposes and a single district can sit across a council boundary, so your postcode does not tell you which authority you pay.
Why is there no CB20 postcode district?
CB20 is not in use. Postcode districts are allocated as sorting requirements change rather than numbered straight through, and a code that is retired or never brought into service is not reissued, so gaps in the sequence are normal.