If you have ever wanted to be like BBC TV election pundit Peter Snow and predict the outcome of the election, now is your chance.
Enter each party's share of the vote in the boxes below, click the Go button and the program will calculate what the new Welsh Assembly might look like.
You must enter a percentage of the vote for each of the four main parties. If you do not enter a figure for Others then the program will assume that any percentage left over out of 100 is the value for these parties.
You do not have to enter figures for the Top-Up votes. If you do not then the program will calculate the result using the percentages you supplied for the first column.
Note: This program is based on a model used by leading election experts in the UK but BBC News Online does not suggest it is completely accurate.
The voting system is new and in particular it is difficult to estimate the impact of voters casting two ballots.
In addition, voting patterns in individual constituencies and regions can affect the overall result.
If you use opinion polls as the basis of your figures, then you should be aware that they generally have a margin of error of +/- 3%.