The website tries to help the public understand the General Election system by translating the support levels for each party into actual seats. The aim is to de-mystify a process which is already well-understood by party insiders, making it accessible to anyone who is interested. The site tries to make the least inaccurate prediction possible and is independent of any other organisation.
No. We try our best, but any individual seat could be incorrectly predicted. Also, if the opinion polls are wrong, that will cause more wrong predictions. Usually, about 50 seats are incorrect. Find more about our Tactical Voting model track record in elections since 1992.
Yes. The purpose of our predictions is not to tell people how to vote but to predict the election outcome given that people have told the opinion pollsters how they intend to vote. The site lets voters in a particular seat estimate the local strength of the parties from national trends. The ultimate decision in that seat is determined by those voters and no-one else.
Local factors can be very important. These can include some factors we can measure, such as local council strength, historic general election performance, incumbency, by-election, income, house prices, and multiple deprivation measures. It also includes some things we can't easily measure such as important local issues and candidate personalities. Sometimes, there are seats with exceptional local factors, such as a prominent independent candidate or minor party running. In rare cases, we will manually adjust our predictions in these seats using external inputs such as information from the betting markets, but this comes with greater uncertainty than normal.
Yes, in the user-defined prediction you can now enter tactical voting parameters. The direction of tactical voting has been measured by us at each election. For example, there may be anti-Conservative or anti-Labour tactical voting, depending on the election. Tactical voting behaviour is different in Scotland, which has recently been along pro-independence/unionist lines rather than a right/left split. Find out more about our Tactical Voting model.
Scotland has six major parties (SNP, Con, Lab, Lib Dem, Reform UK, and the Greens), so needs special handling. Therefore, our model allows all six parties to move dynamically, as measured by the Scottish opinion polls, and our own MRP polling. Scottish polls are shown on the scottish opinion poll page.
Both Reform UK and the Green party are modelled fully in the same way as the other major parties (Con, Lab, Lib and Nationalist parties in Scotland and Wales). Smaller parties such as the Workers Party of Britain are not modelled separately, and are included in the 'Other' category.
The data shown is the snapshot provided by the latest General Election. To keep the consistency of the dataset, it is deliberately not updated to reflect by-elections or changes of party affiliation. This is necessary so that we can predict the next election on the basis of the change in support since the last one. This would make less sense if the base data were measured at different times. Also, by-elections are a poor predictor of general elections, but we do use them sometimes to help predict the next election.
UNS has a worse track record than MRP (Multi-level Regression and Post-stratification). Electoral Calculus no longer uses the Uniform National Swing (UNS) model, since it has serious limitations. You can see details of the current model here (see regression polling). This provides a much better basis for predictions, that allows for regional variation and non-uniform swing. In 2019, we had the most accurate pre-poll predictions: see 2019 case study.
See our articles on regression polling and election prediction.
We update our predictions about once a month, as national opinion polls are published. During a general election campaign, we update our predictions more frequently. You can get email notifications of our updates by subscribing to our mailing list.
We do our own MRP polling from time to time. We also use opinion polls conducted by the major market research companies, and published in the national media. History of recent polls.
Wales, has six major parties (Plaid Cymru, Con, Lab, Lib Dem, Reform UK, and the Greens). Regular opinion polls don't give a lot of detail about Wales, but we periodicially refresh our estimates of Welsh voting patterns through our own MRP polling. See our prediction page for Wales.
This needs regional opinion polls to provide the input data. This can be difficult to obtain. If you have your own regional data, you can use the regional predictor. Sometimes regional data can be derived from aggregating together many polls from the same pollster, though the geographical granularity can be coarse.
We are proud to be one of the few election forecasters to make a prediction in all 650 constituencies in the UK, including the 18 seats in Northern Ireland. We use a UNS model in Northern Ireland, with other relevant inputs, as a different set of parties compete to win seats in Westminster. Northern Irish Westminster voting-intention polls are quite rare, but when they are published they will appear on the Northern Ireland Opinion Polls page.
Absolutely. The Liberal Democrats vote is modelled to allow it to go up or down at the expense of the other two major parties (and the minor parties). The model is fully multi-party and is not a simplistic one-dimensional swing model. Also modelled are the Reform UK and Green parties, plus the SNP (in Scotland) and Plaid Cymru (in Wales).
Our previous model had elements of a Markov transitional model (see model details), but has fewer parameters. Markov models break down the current levels of support for each party according to how that person voted in the previous election. That is, it shows for those who voted (say) Labour in 2015, how many still back Labour, and how many back each of the other parties. The model is interesting conceptually, but it has too many parameters to be calibrated using the published national opinion polls. Regression modelling is generally superior to a purely Markovian approach.
The counties used are historical counties, loosely based on the 1974 boundaries. There are some artificial constructs, such as metropolitan urban areas (eg Manchester, Birmingham, Bristol, Newcastle, Glasgow, Edinburgh), and occasional simplifications, such as keeping the Isle of Wight in Hampshire. Each London borough is classified as its own county. See full details of area and county composition with map.
The Battlemap is less powerful than the full multi-party model as it is only two-dimensional. This means that only the three major parties can move, and the minor parties are assumed to stay fixed. It is easier to use the multi-party model to make your own predictions.
Either because you have spotted it before we have, or because it is not considered a high-quality poll from a non-partisan sponsor.
If you do see a poll we haven't used yet (including any for Scotland or Wales) please email us the details.
We are very happy to predict other elections, when commissioned to do so. Please see our Election Prediction Services.
Local parties have permission to republish data extracts from the 'Overview' section of the seat details page, subject to conditions.
Only data from the 'Overview' section can be re-published, including screenshots or re-typeset material. Attribution must be given to 'Electoral Calculus' and should include the date on which the data was observed, such as "Source: Electoral Calculus, retrieved 1 Jan 2024".
Please bear in mind that our predictions update regularly, and that old predictions can become out-of-date quickly. Local parties should not continue to re-publish out-of-date predictions. Other parties may object to such behaviour, and Electoral Calculus will only endorse and validate our current live prediction in the event of a dispute.
For re-publication of other materials, or for any questions, please contact us at .