Senedd seat calculator
Project seats at the next Senedd election using proportional representation across 16 constituencies and 96 seats
Last election · Final results
Senedd 2026
| Party | Vote share | Votes | Seats |
|---|
Since 2026, the Senedd uses closed-list proportional representation. Wales is divided into 16 constituencies, each electing 6 MSs, for 96 seats total. A party needs 49 seats for a majority. Voters cast one vote for a party list.
Vote share inputs
Use the buttons to load polling data, or drag the sliders to enter custom vote shares.
Projected Senedd
96 MSs total - 49 for a majority
Change since the 2026 election
Projected seats and vote shares against the 7 May 2026 Senedd result. Vote changes are in percentage points.
| Party | 2026 | Projected | Seat change | Vote share |
|---|
Constituency map
Seat allocation by constituency
Marginal seats
The closest races for the final seat in each constituency, ranked by margin. These update dynamically as you change vote shares above.
The 2026 result against polls since the election
Each line joins the seats a party won on 7 May to the seats projected from the average of polls published since. Diamonds are the actual result, circles are the post-election average.
Projected seats from each poll
Seats each poll would have produced under the 96-seat proportional system, through the 7 May 2026 election.
The 5-poll average restarts at 7 May 2026, so post-election polls are never averaged with pre-election ones. Diamonds mark the actual result.
How this calculator works
How does proportional representation work for the Senedd?
Since 2026, the Senedd uses a closed-list proportional representation system with the D'Hondt method. Wales is divided into 16 constituencies, each electing 6 Members of the Senedd (MSs), for a total of 96 seats. Voters cast one vote for a party list in their constituency. A party needs 49 seats for a majority.
How are seats awarded in each constituency?
In each constituency the six seats are allocated one at a time using the D'Hondt method. At every round each party's vote total is divided by one plus the number of seats it has already won, and the party with the highest resulting number takes the next seat.
What does this calculator project?
It projects how a set of Wales-wide vote shares would translate into seats under the 96-member system. The starting point is the actual 7 May 2026 result in each of the 16 constituencies. A party that has fallen nationally since then loses the same proportion of its vote in every constituency. A party that has risen gains the same number of points everywhere, adjusted for local demographics: Plaid Cymru gains less where more of the population is aged 65 or over, and Reform UK gains more where the 2016 Leave vote was higher. The shares are renormalised and D'Hondt allocates the six seats. Tested against the 2026 election from the 2024 general election baseline, this method missed constituency vote shares by 1.4 points on average, against 2.4 for uniform swing. Feeding in the 2026 national shares reproduces the 2026 result exactly.
Can I enter my own vote shares?
Yes. Drag the sliders or type into the boxes in the vote share inputs section. The values are normalised to 100 per cent before seats are calculated, so they do not have to sum exactly.
Result: Senedd Research, Senedd election 2026, compiled from Returning Officer returns. Polls: every published Senedd voting intention poll.