Senedd Seat Calculator
Senedd 2026 Seat Trends
Values use a 3 point moving average.
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Senedd Seat Totals
Constituency Breakdown
Methodology Section
Senedd 2026 system: 96 Members of the Senedd (MSs) are elected from 16 constituencies, each returning 6 MSs using closed-list PR (D’Hondt).
- Each constituency’s six seats are awarded one-by-one to the party with the highest D’Hondt quotient (votes ÷ (1 + seats already won)).
How this calculator works: We take the selected poll’s party shares and project them to each of the 16 constituencies by blending 2021 regional list vote baselines (from the five 2021 regions) using a 2026→2021 region mapping for each constituency. We then apply a national swing (poll minus 2021 total regional baseline) to those blended baselines, and run D’Hondt for 6 seats per constituency. Senedd seat totals are the sum across the 16 constituencies.
- Baselines: 2021 regional list shares (Lab, Con, Plaid, LD, Green, Reform, Others).
- Mapping: each 2026 constituency is linked to one or more 2021 regions (weighted).
- Projection: baseline + national swing
- Seat allocation: D’Hondt per constituency (6 seats).
What is D’Hondt?
The D’Hondt system is a method for turning votes into seats under proportional representation.
Bigger parties usually get more seats, but smaller parties can still win if they have enough votes.
It works by dividing each party’s votes in rounds and awarding seats to whoever has the biggest number at each step.
D’Hondt example (5 candidates, 6 seats)
Illustrative votes: A 40,000 • B 25,000 • C 20,000 • D 10,000 • E 5,000.
- Round 1 (highest quotient): A 40,000 → A gets seat 1 (A:1).
- Round 2: B 25,000 → B gets seat 2 (B:1).
- Round 3: C 20,000 → C gets seat 3 (C:1).
- Round 4: A 40,000/2 = 20,000 → A gets seat 4 (A:2).
- Round 5: B 25,000/2 = 12,500 (beats C 10,000; D 10,000; E 5,000) → B gets seat 5 (B:2).
- Round 6: A 40,000/3 ≈ 13,333 (beats C 10,000; D 10,000) → A gets seat 6 (A:3).
Final seats: A 3, B 2, C 1, D 0, E 0.