There are three swingometers to measure the effect of a vote shift between any two of the three main parties, and they all work the same way.

To measure the effect of a given swing, select one of the dropdown menus in the panel located on the right hand side and then choose a percentage figure.

DEFINITION OF SWING The swing from Party A to Party B is the average of the percentage point fall in Party A's share of the vote and the percentage point rise in Party B's Source: House of Commons Library

Select the Labour dropdown for a swing to Labour, select the Conservative dropdown for a swing to the Conservatives and select the Liberal Democrat dropdown for a swing to the Liberal Democrats.

After selecting a percentage figure and releasing the mouse, the result for that swing will be displayed on the left.

You will see the party predicted to win an overall majority in the House of Commons, and the size of that majority.

You will also see the predicted number of seats won by each party in the Commons and the names of any constituencies predicted to fall on the swing you have chosen.

Any VIPs predicted to be at risk will also be listed, together with information about past elections with similar swings (if any).

Things to remember

The swingometer is not an exact measure, it just gives an indication of what may happen.

Note that the predicted results are calculated using notional figures for Scottish constituencies to take into account the effect of boundary changes at this election.

Experts have estimated for us who would have won each of the changed seats on its new boundaries. The changes mean that the numbers of House of Commons seats shown on a 0% swing are not quite in line with the state of the parties today. Labour - for example - lose a number of seats because of the boundary changes.

Also note that for a number of constituencies, a swing from one party to another can mean a third party gains that seat.

For example, in Labour-held Cardiff Central a 2% swing to the Conservatives will mean the constituency falls to the Liberal Democrats first, as they were a close second there at the 2001 general election. Only on a 21% swing will the third-placed Conservatives gain the seat. Such seats are marked with an asterisk where they are listed.