JFDI Blog

Tag: UK

  • How to make a UK constituency map from a spreadsheet

    How to make a UK constituency map from a spreadsheet

    To make a map of UK parliamentary constituencies, you need a spreadsheet with one column of constituency names (or ONS codes such as E14001063) and one column of values. Paste it into the JFDI map maker and you get a map of all 650 Westminster seats, drawn on the July 2024 boundaries, without signing up or uploading anything.

    Open the map maker

    This guide walks through it with real data, then covers the problems that trip most people up: old boundaries, spelling differences and party colours.

    What you need

    A table with two columns is enough (these values are made up):

    ConstituencyValue
    Aberafan Maesteg41.2
    Aberdeen North38.7
    Aberdeen South44.0

    The first row should be a header. The values can be numbers (turnout, majority, population, a survey score) or words (the winning party, Leave or Remain). Words make a map of categories, each with its own colour.

    You don’t need to tidy the names first. The map maker recognises constituencies by name however they’re written, and by their nine-character ONS code. If your file has both, that’s fine too.

    Step by step

    1. Open the map maker and paste your cells into the box (copy them straight from Excel or Google Sheets), or drop a CSV or Excel file onto the page.
    2. Check the match count. The Data section says which map it chose and how many rows matched. For constituency data, it picks Constituencies as hexagons (2024) by default.
    3. Fix anything unmatched. Press Fix to see rows it couldn’t place. Typos come with a suggestion you can accept in one click.
    4. Choose colours and a title. Under Colours, pick a light-to-dark set for numbers, or keep the automatic colours for categories.
    5. Download it as PNG, SVG or PDF, or copy the embed code for a web page.
    A hexagon map of all 650 UK constituencies, shaded by population
    Every constituency gets one hexagon. This one shows each seat’s population, from ONS small-area estimates.

    Hexagons or real shapes?

    You get hexagons by default because they’re fairer for constituency data. Constituencies have roughly equal numbers of voters, but very unequal areas. Caithness, Sutherland and Easter Ross covers about 11,600 km², more than seven times the area of all 75 London seats put together (about 1,570 km²). On a normal map, the big rural seats dominate and you can barely see the cities.

    On the hexagon map, which uses the House of Commons Library’s layout, every seat is the same size. Switch to real boundaries under Data › Map › Constituencies (2024) if you want geography instead. There’s more on this choice in Hex maps vs real maps: why election maps use hexagons.

    Election results get party colours

    If your values are party names (Labour, Conservative, Liberal Democrat, SNP, Plaid Cymru, Reform UK, Green and so on), the map uses each party’s usual colour, as election maps on TV do. You can switch to any other colour set under Colours.

    Common problems

    “Some of my constituencies don’t match”

    The most common cause is old boundaries. Constituency boundaries changed at the July 2024 general election, and data from before then (including the 2019 results) uses the old seats. The map maker recognises the old ONS codes and tells you they’re from the previous boundaries, rather than quietly putting them in the wrong place.

    Many names didn’t change in 2024, so a file can match almost perfectly and still be on old boundaries. Check the date of your data before you publish.

    “It picked the wrong map”

    If your table mixes levels (some councils, some constituencies), the map maker picks the level with the most matches. Choose the map yourself under Data › Map.

    Totals and rates

    If you’re mapping a count, such as the number of people claiming a benefit, compare like with like. Constituencies have similar electorates but not identical populations, so a rate (per 1,000 people, or a percentage) is usually fairer than a raw count. The map maker spots columns that look like totals and suggests a rate. Our explainer on what a choropleth map is and when it misleads goes into why.

    Where the boundaries come from

    The 2024 constituency boundaries are the Office for National Statistics’ generalised boundary files, published under the Open Government Licence, and the hexagon layout is the House of Commons Library’s, under the Open Parliament Licence. The map carries the required credit at the bottom; keep it if you crop the image. You can use the maps commercially.

    Is my data private?

    Yes. The map is drawn inside your browser, and the spreadsheet never leaves your device. That matters if you’re mapping unpublished polling, membership lists or canvassing returns. If you make a share link, the data travels inside the link itself, so treat the link like the data.

    Related

  • Map of the month: equal electorates, very unequal populations

    Map of the month: equal electorates, very unequal populations

    Westminster constituencies were drawn to have nearly equal numbers of voters, but the number of people living in them varies almost twofold. Leaving aside five protected island seats, the smallest constituency by population, Congleton, has about 84,000 residents; the largest, Cities of London and Westminster, has about 163,000. Thirty-one of the fifty most populous seats are in London.

    Make your own constituency map
    A hexagon map of UK constituencies shaded by population, with the darkest hexagons concentrated in London and major cities
    Population of each Westminster constituency (2024 boundaries). One hexagon per seat. Source: ONS small-area population estimates (mid-2019), via mySociety.

    The rule: equal electorates

    For the 2023 boundary review, which set the seats used at the July 2024 general election, each constituency had to have between 69,724 and 77,062 registered electors, within 5% of a quota of 73,393, based on the electoral register of 2 March 2020. Five island seats were protected from the rule: the two Isle of Wight seats, Na h-Eileanan an Iar, Orkney and Shetland, and Ynys Môn (2023 review).

    So every MP outside the islands represents roughly the same number of voters. They don’t represent the same number of people.

    The numbers

    Across the 645 seats subject to the rule:

    Population
    Smallest (Congleton)83,907
    10th percentile92,181
    Median100,479
    90th percentile117,075
    Largest (Cities of London and Westminster)162,641

    The ten most populous seats are:

    ConstituencyPopulation
    Cities of London and Westminster162,641
    Birmingham Ladywood157,574
    Kensington and Bayswater147,231
    Hampstead and Highgate144,676
    Poplar and Limehouse141,599
    Erith and Thamesmead139,649
    Tottenham138,358
    Holborn and St Pancras137,909
    Bethnal Green and Stepney135,919
    Coventry South135,355

    And by region, the average London seat has about 119,000 residents, against about 96,000 in Scotland and 97,000 in the South West.

    Why the gap?

    Equal electorates and unequal populations aren’t a contradiction: lots of residents aren’t on the electoral register. The seats with the most people per voter tend to share features that are likely to explain much of it:

    • Children. Under-18s can’t vote in general elections, so seats with more young families have more residents per elector.
    • People who can’t vote in general elections. Most foreign nationals, including most EU citizens, can’t, while Irish and qualifying Commonwealth citizens can. Seats with many residents from elsewhere have fewer electors per head.
    • People who aren’t registered. Registration rates are lower among renters, people who move often and students, all common in inner cities.
    • Timing. The populations here are mid-2019 estimates and the electorates come from March 2020; places growing fast have moved on since.

    This data can’t separate these effects, so treat them as likely contributors rather than a measured breakdown.

    What it means

    Equal electorates are the legal standard, and there are good arguments for it: MPs are elected by voters. But MPs also serve residents who can’t vote, taking up their casework and representing them in Parliament. An MP for Birmingham Ladywood represents nearly twice as many people as one for Congleton.

    How this map was made

    The population figures are the ONS’s mid-2019 small-area estimates, added up for each 2024 constituency by mySociety, and they’re built into the JFDI map maker: it’s the UK constituencies example on the start page. The map uses the House of Commons Library’s hexagon layout, so every seat is the same size. On a normal map, London’s 75 seats would cover less than 1% of the picture; see why election maps use hexagons.

    Open the example, change the colours, switch to real boundaries or add your own data, and download it. Every map you make is yours to use, with the boundary credit kept at the bottom.

    Map of the month takes a public dataset each month and maps it. Suggestions are welcome.

    Related

  • Hex maps vs real maps: why election maps use hexagons

    Hex maps vs real maps: why election maps use hexagons

    Election maps use hexagons because constituencies have roughly equal numbers of voters but wildly unequal areas. On a normal map, a handful of huge rural seats fill most of the picture and the cities shrink to specks. A hex map gives every seat one identical hexagon, so the picture shows seats, which is what decides an election.

    Make a hex map of your data

    The numbers behind the distortion

    I added up the areas of all 650 Westminster constituencies on the July 2024 boundaries (ONS boundary files):

    AreaSeatsShare of seatsShare of UK land
    London7511.5%0.6%
    Scotland578.8%32%
    Rest of the UK51879.7%67%

    London elects more MPs than Scotland, yet on a normal map Scotland takes up about fifty times as much space. Fifty-nine seats are smaller than 20 km², while the largest, Caithness, Sutherland and Easter Ross, covers about 11,600 km². Colour each seat by the winning party and the map mostly shows who won the Highlands.

    The same constituency data drawn as real boundaries and as hexagons
    The same data both ways. On the left, real boundaries; on the right, one hexagon per seat.

    What a hex map is

    A hex map is a kind of cartogram: a map where the size of each area stands for something other than land. Here, each constituency is one hexagon, placed roughly where it really is so neighbours stay neighbours. London becomes a recognisable cluster, and you can see every seat in Manchester or Glasgow.

    The layout used in the JFDI map maker is the House of Commons Library’s, the same one many newsrooms use. It’s published under the Open Parliament Licence.

    When to use hexagons

    Use a hex map when each area counts equally in what you’re showing:

    • election results and vote shares
    • polling or MRP estimates by seat
    • anything per constituency that an MP or campaign will act on, such as casework or survey responses

    Use real boundaries when geography matters:

    • something physical, such as flood risk, broadband coverage or distance to a hospital
    • when readers need to find a specific place by shape or coastline
    • local data within one region, where size differences are smaller

    The trade-offs

    Hex maps aren’t free of distortion; they move it somewhere else.

    • Shapes and positions are approximate. A seat may sit a hexagon away from where you expect. Labels or a hover tooltip help people find their own.
    • Population isn’t exactly equal. Seats were drawn to have electorates within 5% of 73,393 (with five protected island seats excluded), but total population, including children and people not registered, varies much more.
    • Readers need a moment. Add a subtitle such as “One hexagon per constituency” so nobody mistakes it for geography.

    Councils: a different kind of cartogram

    Local authorities vary in population as well as area, from the Isles of Scilly to Birmingham, so one hexagon each would be unfair the other way. For councils, the map maker offers Local authorities sized by population, also from the House of Commons Library, where each council is built from small hexagons of about 8,000 people. Big cities get room in proportion to their residents.

    How to switch

    In the map maker, load your constituency data, then open Data › Map and choose between Constituencies (2024) and Constituencies as hexagons (2024). Your colours, title and data carry over, so you can download both and compare them. The step-by-step guide covers getting your data in.

    Sources

    • Constituency areas: ONS Westminster Parliamentary Constituencies (July 2024) boundaries, Open Government Licence.
    • Electoral quota: 2023 review of Westminster constituencies.
    • Hexagon layout: House of Commons Library, Open Parliament Licence.