Seat Projection Calculator
Adjust party vote percentages and see how seats shift in the parliament. Compare FPTP and PR systems side by side.
| Party | Vote % | Seats |
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How Seat Projections Work
Understand the difference between electoral systems.
Proportional Representation
Seats are allocated in proportion to vote share. A party with 30% of the vote gets about 30% of the seats. Used in many European and Latin American countries.
First Past the Post
The party with the most votes in each district wins the seat. Often leads to majority governments with less than 50% of the popular vote. Used in the UK, US, and India.
Mixed Systems
Some countries use hybrid systems combining FPTP and PR elements. Germany and New Zealand use Mixed-Member Proportional representation for more balanced outcomes.
Frequently Asked Questions
Common questions about seat projection and electoral systems.
First Past the Post (FPTP) awards seats to the candidate with the most votes in each district. Proportional Representation (PR) allocates seats based on each party's total vote share, producing more proportional outcomes that better reflect the electorate's preferences.
Under PR, seats are allocated in proportion to each party's vote percentage. If a party wins 30% of the vote, they get roughly 30% of the total seats, subject to the divisor method used. This calculator uses a simplified proportional allocation similar to the D'Hondt method.
Yes. Click on any party label and type your own party name. The sliders, seat diagram, and results table update with your custom names in real time.
The calculator normalizes percentages so they always sum to 100% for seat allocation. Any unassigned percentage is treated as votes for "Other" parties not shown in the diagram.
The PR mode uses a simplified proportional allocation similar to the D'Hondt method used in over 40 countries. The FPTP mode is a simplified winner-take-all model representing how single-member district elections work.