YO postcode district map, York

Where the YO districts sit

10 districts are plotted without a label where labels would overlap; every one is in the table below.

Where YO sits

It falls across North Yorkshire, York and East Riding of Yorkshire.

Water supply across YO

All 30 YO districts are supplied by Yorkshire Water, which is notable at this size: an area with this many districts usually crosses at least one supply boundary, and this one does not.

No hosepipe ban currently applies anywhere in YO.

The shape of the YO area

The districts are wildly uneven: YO25 holds 1,403 postcodes around Driffield and YO90 holds 10, a ratio of about 140 to one. They divide into 116 sectors.

The numbering is not continuous. YO runs up to 90 but has only 30 districts, so 60 numbers are unused:.

Several districts share a settlement, which is a common source of confusion when a form rejects an address: YO1, YO10, YO19, YO23, YO24, YO26, YO30, YO31 and YO90 all point at York, YO11, YO12 and YO13 all point at Scarborough and YO15 and YO16 all point at Bridlington.

What borders YO

YO sits next to HU (Kingston upon Hull) to the south east, HG (Harrogate) to the west, TS (Middlesbrough) to the north west, LS (Leeds) to the south west and WF (Wakefield) to the south west.

Its neighbours run in 4 different directions, so YO is landlocked by other postcode areas on most sides.

YO 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 YO

Figures are in milligrams per litre as calcium carbonate, the unit UK water companies report in. 27 of 30 districts have a published figure.

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 Yorkshire Water drinking water quality data, via Stream, licensed under CC BY 4.0. Edition 2026, published 1 January 2026. Yorkshire Water publishes this as mg/l without naming the species. We read it as calcium carbonate because the determinand is Hardness total and the dataset contains no calcium determinand. Evidence: determinand "Hardness total"; DWI code "HARD T"; no calcium determinand published in the dataset.

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 YO 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.

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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