I occasionally get asked questions about the UK postcode data I provide on the site, so I thought I'd give the answers to some of the common ones here.
If I download the CSV file containing all postcodes, not all the rows are displayed when I open it in Excel, where's the rest of the data?
Excel 2003 and earlier can only display 65,536 rows of data in a file. Excel 2007 and later can display 1,048,576 rows. Unfortunately neither can handle the full postcode CSV file. You've got a few options. You can download the CSV files for specific areas that contain fewer rows. Or you can try out this tool from Tony Wilk or if you've got Excel 2010, try out PowerPivot. I've not used either of these tools, but believe they should help. Alternatively, you can open the file in a text editor. And finally, if you would like the data in another format, let me know what would be useful and I'll see what I can do.
Where does the data come from?
Most of the data comes from the Office of National Statistics (ONS) under the Open Government Licence. You can download the data set directly from them.
Why are the GY, IM and JE districts missing?
The ONS data includes the GY, IM and JE districts, but does not include the locations of these postcodes, so I haven't added them. As yet I've been unable to source the data for these postcode areas.
Postcode XX1 2ZZ isn't in the data, why not?
It might be you've got an old postcode that has been removed from the data. Check the postcode on the Royal Mail website to see if it's still in use. Alternatively, your postcode may be newer than the ONS data, which is only updated every three months.
Postcode XX1 2ZZ isn't in the data but if I use the geocoding tool, I get a location returned, why?
The geocoding tools don't use the same database to do their work, they use the Google Maps geocoding API. From my experience, this API will return an approximate location for a postcode, even if the postcode doesn't exist. For example if XX1 2ZZ doesn't exist, the Google Maps geocoding API will return the general location of the XX1 postcode area.
Some postcodes have the same latitude and longitude, why is that?
Generally this will be because the postcodes are non-geographical postcodes, used for PO boxes etc. The latitude and longitude provided will be the location of the associated post office.
The address shown on the map for a postcode doesn't match up with the postcode, why?
The approximate address comes from the Google Map reverse geocoding service so the postcode may not match up with the original postcode you were looking at. This will often occur when you're looking at a non-geographical postcode which shares its location with several other postcodes.
What datum is used for the latitude and longitude?
The latitudes and longitudes use the WGS84 datum.
Why does the Northern Irish data use GB grid references instead of Irish grid references?
Northern Ireland isn't part of the GB grid reference system so the values shown are artificial (although Northern Ireland could fit within the GB grid system) but I figured that was a preferable solution than the data using inconsistent systems.
Can the approximate address for each postcode be included in the CSV download?
The short answer is no. The longer answer is the address shown when viewing a postcode comes from the Google Maps service so isn't stored on this website. I have looked at pulling these addresses out of Google Maps and storing them locally but I'm unsure if this breaks their licensing rules and also calculated it would take about 2 years to complete due to usage limits.
The other issue to consider is that each postcode can have multiple addresses, so the approximate address may not be that useful to you. If you need address level information for postcodes, you'll need to purchase the PAF dataset from Royal Mail or one of its resellers.
How do I find the postcode for a particular address?
If you know the full address, then the Royal Mail website is your best bet. If you want to find the likely postcode for a particular area, you can use my Postcode Finder page.
The location shown for postcode XX1 2ZZ is incorrect, who should I contact?
Mistakes happen, but the chances are the problem is in the source data I use to populate the website, rather than being a problem with the site. Generally these errors are corrected in the next upload, but if you want to tell someone, the Royal Mail are the original source of postcode data.
How often is the data updated?
The ONS update their data every three months. I try and update the site as soon as possible after it comes out.
Why do some postcodes have no latitude and longitude?
These are non-geographic postcodes which may be used for PO Boxes and similar and don't have an associated location