SG3 postcode district: Knebworth and around, Hertfordshire
SG3 is a postcode district in Hertfordshire, with 206 postcodes in use in 1 sector. It has postcodes in Knebworth and Woolmer Green. It is split between 3 councils: North Hertfordshire (119 postcodes), Welwyn Hatfield (49) and East Hertfordshire (38).
- Postcodes in use
- 206
- Sectors
- 1
- Councils
- 3 councils
- Places
- 2 places
Source: ONS Postcode Directory, August 2026, loaded 20 October 2026.
Every postcode in SG3, by gigabit broadband
- No home or business can get gigabit: 36
- Some can get gigabit: 25
- Every home and business can get gigabit: 142
- Ofcom gives no figure: 3
- Outline: where 5 or more postcodes without gigabit lie together
Of the 206 postcodes in SG3 that ONS places, 36 have no home or business that can get gigabit, 25 have some that can, 142 can all get it and 3 have no Ofcom figure.
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. A dashed outline shows where 5 or more lie within 180 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 51.8603, longitude -0.1825. Open this area on OpenStreetMap
Sources: ONS Postcode Directory, August 2026, loaded 20 October 2026; Ofcom Connected Nations, Connected Nations, Spring 2026; roads, rivers and built-up areas: Ordnance Survey open maps. 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.
Postcodes without gigabit
36 postcodes here have no gigabit. These are the 12 first in postcode order.
2 further out, not drawn
These postcodes lie well apart from the rest, so the map is drawn without them to show the rest closer; they are in every count.
What broadband can you get in SG3?
Ofcom reports on 203 of the 206 postcodes in SG3. At 142 of them every home and business can get gigabit broadband.
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 checkerSource: Ofcom Connected Nations, Connected Nations, Spring 2026, data for January 2026.
Is SG3 at risk of flooding?
None of the 206 postcodes in SG3 is on the Environment Agency's list of postcodes with a home or business in an area at risk of flooding from rivers or the sea.
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 flood risk, published 6 July 2026.
What do homes sell for in SG3?
Homes in SG3 sold for a typical £462,500 in the 12 months to September 2026, across 93 sales, HM Land Registry's figures show. The 12 months before gave £473,750 from 164 sales: not a change larger than chance would explain, given which homes happened to sell.
- Detached £800,000 17 sales
- Semi-detached £550,000 27 sales
- Terraced £400,000 28 sales
- Flat or maisonette £255,000 21 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 October 2026.
Postcodes in SG3
Pick a sector, then a postcode. A sector is the district plus the next digit.
UK postcode format explainedPlaces in SG3
Towns and villages with postcodes in SG3, and how many each has here.
Who covers SG3
How many of the district's postcodes in use fall under each council, constituency and police force area.
Councils
What council am I in?Constituencies
- Stevenage156
- Welwyn Hatfield49
- North East Hertfordshire1
Police force areas
- Hertfordshire206
Next to SG3
"Next to" is by number: the districts before and after SG3 in the SG area.
Check a postcode
Where the facts on this page come from
- Office for National Statistics: ONS Postcode Directory
- Ofcom Connected Nations
- Environment Agency flood risk
- HM Land Registry Price Paid Data
Contains public sector information licensed under the Open Government Licence v3.0. Contains HM Land Registry data © Crown copyright and database right 2021. This data is licensed under the Open Government Licence v3.0.
Licence: Open Government Licence v3.0.
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