UK Seat Projection Calculator
Adjust each party’s vote share and see projected Westminster seats in real time, using uniform swing from the 2024 General Election.
Set Vote Shares
Adjust sliders to set each party’s national vote share. Total must be close to 100%. Projections update in real time using Uniform National Swing (UNS) from the 2024 GE baseline.
Projected Seats (650 total)
Parliament Composition
Proportional bar showing seat distribution across all 650 constituencies.
How this calculator works — and its limitations
This tool uses Uniform National Swing (UNS): it takes the 2024 General Election result as a baseline and applies the same swing in every constituency. For example, if Labour’s national share falls by 5 points, it falls by exactly 5 points in every seat — from Islington North to Clacton.
Real elections do not work this way. Actual seat outcomes are shaped by local factors, incumbent effects, tactical voting, demographic change, and regional variation. A 5-point national swing for Reform UK will produce very different results in a constituency where they polled 8% in 2024 versus one where they polled 32%.
For more sophisticated projections, MRP polling models each constituency individually. First Past the Post also means that small changes in vote share can produce dramatically different seat outcomes depending on how votes are distributed geographically.