2029 Seat Projection Calculator
Adjust each party’s vote share and see real-time seat projections using uniform swing from the 2024 General Election. Pre-filled with May 2026 polling averages.
Using the Calculator
Sliders are pre-set to May 2026 polling averages. Move any slider to adjust a party’s national vote share. The model applies Uniform National Swing (UNS) from the 2024 GE result across all 650 constituencies. Keep the total close to 100%. Projections update in real time.
Set Vote Shares — 2029 Scenario
Projected Seats
How the Model Works
Uniform National Swing
UNS assumes each party’s vote share changes by the same amount in every constituency. If Labour falls 15 points nationally, they lose 15 points in every seat. This is a simplification — in reality, swing varies considerably.
Why UNS underestimates Reform
Reform’s vote is more geographically concentrated in certain English seats than UNS implies. MRP polls typically project more seats for Reform at a given vote share than UNS would suggest. Use this tool as a baseline, not a forecast.
2024 Baseline
The 2024 result: Lab 412 seats (33.7%), Con 121 (23.7%), Reform 5 (14.3%), LD 72 (12.2%), Green 4 (6.7%), SNP 9 (2.5%). This is what the model swings from. All 650 constituencies are modelled using this starting point.