Senedd Seat Calculators
Senedd 2026 Seat Trends
Values use a 3 point moving average where available.
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Senedd Seat Totals
Constituency Breakdown
Methodology Section
Senedd: How the system works
For the 2026 election, the Senedd will have 96 Members of the Senedd (MSs). Wales is divided into 16 constituencies, and each constituency elects 6 MSs. Seats are allocated using closed-list proportional representation with the D'Hondt method.
How seats are awarded
In each constituency, the six seats are allocated one at a time. At every round, each party's vote total is divided by 1 + the number of seats it has already won. The party with the highest resulting number takes the next seat.
How this calculator works
Start with the poll.
We take the party vote shares from the selected poll.
Map constituencies to 2021 regions.
Each of the 16 new 2026 constituencies is linked to one or more of the five 2021 Senedd regions. These links are weighted so each constituency inherits a baseline from the most relevant 2021 regional results.
Blend the 2021 baselines.
For each constituency, we create a starting point based on the 2021 regional list vote shares (Lab, Con, Plaid, Lib Dem, Green, Reform, Others).
Apply a differential swing.
We compare the poll's overall vote shares with the 2021 Wales-wide regional totals, then apply a differential swing model that adjusts the magnitude of vote changes based on each party's historical strength in each constituency. Parties gain more in their strongholds and less in historically weak areas, preventing unrealistic over-projections in areas where they traditionally have low support.
Run D'Hondt locally.
Once each constituency has projected vote totals, we run the D'Hondt method to allocate its six seats.
Add everything up.
Final Senedd totals are simply the sum of all 16 constituency allocations.
What is D'Hondt?
D'Hondt is a way of turning votes into seats under proportional representation. Larger parties tend to win more seats, but smaller parties can still gain representation if they have enough votes.
The system works in rounds. In each round, every party's vote total is divided by a number that increases as they win seats. The party with the highest score wins the next seat.
Example (five parties, six seats)
Votes: A 40,000 • B 25,000 • C 20,000 • D 10,000 • E 5,000
- Seat 1: A (40,000)
- Seat 2: B (25,000)
- Seat 3: C (20,000)
- Seat 4: A (40,000 ÷ 2 = 20,000)
- Seat 5: B (25,000 ÷ 2 = 12,500)
- Seat 6: A (40,000 ÷ 3 ≈ 13,333)
Final result: A 3 seats, B 2, C 1, D 0, E 0.