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. 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. Population and household data comes from the 2011 census, property sales data is from the Land Registry. Links to all the data is available from the links page. All the data can be reused with the relevant attribution.
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.
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.
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.
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