SN postcode district map, Swindon
Supplier statuses last checked .
The SN postcode area covers 21 districts and 14,710 live postcodes, from SN1 to SN99. It is centred on Swindon and also covers Corsham, Chippenham, Marlborough, Devizes and Royal Wootton Bassett.
Districts here average 700 postcodes.
Where the SN districts sit
4 districts are plotted without a label where labels would overlap; every one is in the table below.
Where SN sits
It is administratively fragmented, reaching into Wiltshire, Swindon, Oxfordshire and South Gloucestershire and 0 other authorities.
Water supply across SN
All 21 SN districts are supplied by Wessex Water. That makes SN simple in a way many areas are not: one company, one set of rules, one status to check.
Wessex Water has a hosepipe ban in force from 18 August 2026, covering the whole of SN.
The shape of the SN area
The districts are wildly uneven: SN15 holds 1,316 postcodes around Chippenham and SN80 holds 1, a ratio of about 1316 to one. They divide into 96 sectors.
The numbering is not continuous. SN runs up to 99 but has only 21 districts, so 78 numbers are unused:.
Several districts share a settlement, which is a common source of confusion when a form rejects an address: SN1, SN2, SN3, SN5, SN25, SN38 and SN99 all point at Swindon, SN6 and SN26 all point at Highworth and SN8 and SN9 all point at Marlborough.
SN80 is a non-geographic district: it carries no coordinates because it is used for PO boxes and large users rather than for streets. It appears in the table below but cannot be placed on the map.
What borders SN
SN sits next to GL (Gloucester) to the north west, SP (Salisbury) to the south, BA (Bath) to the south west, RG (Reading) to the east and BS (Bristol) to the west.
Its neighbours run in 5 different directions, so SN is landlocked by other postcode areas on most sides.
SN districts, settlements and water supply
| District | Principal settlement | Water company | Hosepipe ban status |
|---|---|---|---|
| SN1 | Swindon | Wessex Water / Thames Water | Ban in force |
| SN2 | Swindon | Wessex Water / Thames Water | Ban in force |
| SN3 | Swindon | Wessex Water / Thames Water | Ban in force |
| SN4 | Royal Wootton Bassett | Wessex Water / Thames Water | Ban in force |
| SN5 | Swindon | Wessex Water / Thames Water | Ban in force |
| SN6 | Highworth | Wessex Water / Thames Water | Ban in force |
| SN7 | Faringdon | Wessex Water / Thames Water | Ban in force |
| SN8 | Marlborough | Wessex Water / Thames Water | Ban in force |
| SN9 | Marlborough | Wessex Water / Thames Water | Ban in force |
| SN10 | Devizes | Wessex Water / Thames Water | Ban in force |
| SN11 | Calne | Wessex Water / Thames Water | Ban in force |
| SN12 | Melksham | Wessex Water / Thames Water | Ban in force |
| SN13 | Corsham | Wessex Water / Thames Water | Ban in force |
| SN14 | Corsham | Wessex Water / Thames Water | Ban in force |
| SN15 | Chippenham | Wessex Water / Thames Water | Ban in force |
| SN16 | Malmesbury | Wessex Water / Thames Water | Ban in force |
| SN25 | Swindon | Wessex Water / Thames Water | Ban in force |
| SN26 | Highworth | Wessex Water / Thames Water | Ban in force |
| SN38 | Swindon | Wessex Water / Thames Water | Ban in force |
| SN80 | — | Wessex Water / Thames Water | Ban in force |
| SN99 | Swindon | Wessex Water / Thames 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 SN
Figures are in milligrams per litre as calcium carbonate, the unit UK water companies report in. 9 of 21 districts have a published figure.
| District | Hardness | As published | Supply zone | Published by |
|---|---|---|---|---|
| SN1 | Not published by Wessex Water. Check with your supplier. | |||
| SN2 | Not published by Wessex Water. Check with your supplier. | |||
| SN3 | Not published by Wessex Water. Check with your supplier. | |||
| SN4 | Not published by Wessex Water. Check with your supplier. | |||
| SN5 | Not published by Wessex Water. Check with your supplier. | |||
| SN6 | Not published by Wessex Water. Check with your supplier. | |||
| SN7 | Not published by Wessex Water. Check with your supplier. | |||
| SN8 | 287 mg/l That is hard on the water industry scale. | 287 mg/l as CaCO₃ | E01031843, E01031847, E01031877 | Wessex Water 2022-2025 edition |
| SN9 | 224.3–331.1 mg/l varies across this district | 265.1 mg/l as CaCO₃ | E01031842, E01031866, E01031869, E01031870 +2 more | Wessex Water 2022-2025 edition |
| SN10 | 338.4 mg/l That is hard on the water industry scale. | 338.4 mg/l as CaCO₃ | E01031846, E01031848, E01031850, E01031851 +15 more | Wessex Water 2022-2025 edition |
| SN11 | 345.7 mg/l That is hard on the water industry scale. | 345.7 mg/l as CaCO₃ | E01031895, E01031896, E01031897, E01031898 +10 more | Wessex Water 2022-2025 edition |
| SN12 | 329.9 mg/l That is hard on the water industry scale. | 329.9 mg/l as CaCO₃ | E01031845, E01031876, E01031942, E01032044 +14 more | Wessex Water 2022-2025 edition |
| SN13 | 327.5 mg/l That is hard on the water industry scale. | 327.5 mg/l as CaCO₃ | E01031888, E01031889, E01031890, E01031929 +8 more | Wessex Water 2022-2025 edition |
| SN14 | 328.3 mg/l That is hard on the water industry scale. | 328.3 mg/l as CaCO₃ | E01031906, E01031909, E01031940, E01031950 +1 more | Wessex Water 2022-2025 edition |
| SN15 | 333.1 mg/l That is hard on the water industry scale. | 333.1 mg/l as CaCO₃ | E01031907, E01031908, E01031911, E01031912 +17 more | Wessex Water 2022-2025 edition |
| SN16 | 314.5 mg/l That is hard on the water industry scale. | 314.5 mg/l as CaCO₃ | E01031885, E01031886, E01031892, E01031893 +6 more | Wessex Water 2022-2025 edition |
| SN25 | Not published by Wessex Water. Check with your supplier. | |||
| SN26 | Not published by Wessex Water. Check with your supplier. | |||
| SN38 | Not published by Wessex Water. Check with your supplier. | |||
| SN80 | Not published by Wessex Water. Check with your supplier. | |||
| SN99 | Not published by Wessex Water. Check with your supplier. | |||
Descriptions such as very soft, soft, moderately hard, hard, very hard are the water industry scale: very soft below 75, soft 75–125, moderately hard 125–250, hard 250–375, very hard above 375 mg/l. Your supplier may use a different scale for the same number.
Contains Wessex Water drinking water quality data, via Stream, licensed under CC BY 4.0. Edition 2022-2025, published 1 January 2025.
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 SN 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 SN area?
There are 21 SN postcode districts, running from SN1 to SN99, and they contain 14,710 live postcodes across 96 sectors.
What towns does the SN postcode area cover?
SN covers Swindon, Corsham, Chippenham, Marlborough, Devizes and Royal Wootton Bassett. The area takes its name from Swindon, and each district is listed with its settlement in the table on this page.
Which water company supplies SN postcodes?
Wessex Water supplies all 21 SN 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 SN1 and SN2 both say Swindon?
SN1, SN2, SN3, SN5, SN25, SN38 and SN99 all serve Swindon, 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.
What is SN80 used for?
SN80 is a non-geographic postcode district. It is used for PO boxes and large users such as banks and government departments that receive enough mail to need their own code, so it has no streets and no position on a map.
Can I download a free SN postcode map?
Yes. This page offers the SN 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 SN area called Swindon when it covers Chippenham?
SN takes its letters from Swindon, where the sorting office that served the area was based when the code was allocated. Chippenham is the largest settlement in the area today, in SN15, but the area code follows the historic sorting geography rather than current population.