A seat projection is an estimate of how many seats each party or candidate will win in a legislature, based on polling data or partial election results. It translates vote share, which is what polls and early counts measure, into seats, which is what decides who forms a government.

Why vote share and seats are different

In most parliamentary systems, winning 40% of the vote does not mean winning 40% of the seats. The relationship depends on the electoral system:

• First-past-the-post systems, such as Canada and the UK, award each seat to whoever wins the most votes locally. A small shift in national vote share can swing many seats.
• Proportional systems, such as Sweden, allocate seats according to vote share, but thresholds and allocation formulas still shape the result. A party just below a threshold can win no seats at all.

A seat projection applies the rules of the specific system to the available vote data.

How seat projections are built

• Before election day, projections typically combine polling averages with past results by district, estimating how a regional swing would change each seat.
• On election night, projections update as real results arrive. Early counts replace polling assumptions district by district, and the projection narrows as more votes are reported.

A projection is not a call. A call declares a winner in a specific race. A projection estimates the overall picture and comes with uncertainty, especially early in the count.

Seat projections on air

Broadcasters usually present seat projections as a seat count or a parliament chart showing each party's share of the chamber, often with a line marking the majority threshold. Analysts then use the projection to discuss what comes next: whether a party can govern alone, or which coalitions would reach a majority.

Why it matters for broadcasters

In parliamentary elections, the seat count is the headline. Viewers want to know who will govern, and a clear, live seat projection answers that question faster than district-by-district results alone. It also sets up the most watched analysis of the night: coalition scenarios.

Related terms

• What is the Magic Wall?
• What is telestration?
• What is data visualization?

IK Election Insights includes live coalition and seat scenario modeling, used by SVT in Sweden to model government formation on election night.