SG postcode district map, Stevenage
Supplier statuses last checked .
The SG postcode area covers 19 districts and 12,179 live postcodes, from SG1 to SG19. It is centred on Stevenage and also covers Hitchin, Royston, Hertford, Letchworth and Ware.
Districts here average 641 postcodes.
Where the SG districts sit
3 districts are plotted without a label where labels would overlap; every one is in the table below.
Where SG sits
It is administratively fragmented, reaching into Hertfordshire, Central Bedfordshire, Cambridgeshire and Essex and 0 other authorities.
Water supply across SG
All 19 SG districts are supplied by Affinity Water. That makes SG simple in a way many areas are not: one company, one set of rules, one status to check.
Affinity Water has a hosepipe ban in force from 11 July 2026, covering the whole of SG.
The shape of the SG area
SG8 is the largest district with 1,299 postcodes around Royston, and SG10 the smallest with 108. The area divides into 63 postcode sectors.
Several districts share a settlement, which is a common source of confusion when a form rejects an address: SG1, SG2 and SG3 all point at Stevenage, SG4 and SG5 all point at Hitchin and SG9 and SG11 all point at Buntingford.
What borders SG
SG sits next to AL (St Albans) to the south west, EN (Waltham Cross) to the south, LU (Luton) to the west, CB (Cambridge) to the north east and WD (Rickmansworth) to the south west.
Its neighbours run in 4 different directions, so SG is landlocked by other postcode areas on most sides.
SG districts, settlements and water supply
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 SG
No water company covering SG 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 |
|---|---|---|---|---|
| SG1 | Not published by Affinity Water. Check with your supplier. | |||
| SG2 | Not published by Affinity Water. Check with your supplier. | |||
| SG3 | Not published by Affinity Water. Check with your supplier. | |||
| SG4 | Not published by Affinity Water. Check with your supplier. | |||
| SG5 | Not published by Affinity Water. Check with your supplier. | |||
| SG6 | Not published by Affinity Water. Check with your supplier. | |||
| SG7 | Not published by Affinity Water. Check with your supplier. | |||
| SG8 | Not published by Affinity Water. Check with your supplier. | |||
| SG9 | Not published by Affinity Water. Check with your supplier. | |||
| SG10 | Not published by Affinity Water. Check with your supplier. | |||
| SG11 | Not published by Affinity Water. Check with your supplier. | |||
| SG12 | Not published by Affinity Water. Check with your supplier. | |||
| SG13 | Not published by Affinity Water. Check with your supplier. | |||
| SG14 | Not published by Affinity Water. Check with your supplier. | |||
| SG15 | Not published by Affinity Water. Check with your supplier. | |||
| SG16 | Not published by Affinity Water. Check with your supplier. | |||
| SG17 | Not published by Affinity Water. Check with your supplier. | |||
| SG18 | Not published by Affinity Water. Check with your supplier. | |||
| SG19 | Not published by Affinity 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 SG 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 SG area?
There are 19 SG postcode districts, running from SG1 to SG19, and they contain 12,179 live postcodes across 63 sectors.
What towns does the SG postcode area cover?
SG covers Stevenage, Hitchin, Royston, Hertford, Letchworth and Ware. The area takes its name from Stevenage, and each district is listed with its settlement in the table on this page.
Which water company supplies SG postcodes?
Affinity Water supplies all 19 SG 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 SG1 and SG2 both say Stevenage?
SG1, SG2 and SG3 all serve Stevenage, 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 SG postcode map?
Yes. This page offers the SG 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.
Why is the SG area called Stevenage when it covers Royston?
SG takes its letters from Stevenage, where the sorting office that served the area was based when the code was allocated. Royston is the largest settlement in the area today, in SG8, but the area code follows the historic sorting geography rather than current population.
Which councils cover the SG postcode area?
SG reaches into Hertfordshire, Central Bedfordshire, Cambridgeshire and Essex. 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.