Holyrood Seat Calculator

Enter your own polling numbers to project constituency and regional list seats for the Scottish Parliament.

Scottish voters cast two separate votes: one for a constituency candidate, one for a regional party list.

73 Constituency seats are decided by FPTP, while 56 Regional List seats are decided by D'Hondt PR.

Enter Polling Numbers (%)

Input separate vote shares for constituency and regional list elections

Constituency Votes

SNP

%

Labour

%

Conservative

%

Liberal Democrats

%

Green

%

Reform UK

%

Alba

%

Others

%
Enter at least two parties and ensure the total equals 100%.

Regional List Votes

SNP

%

Labour

%

Conservative

%

Liberal Democrats

%

Green

%

Reform UK

%

Alba

%

Others

%
Enter at least two parties and ensure the total equals 100%.
Complete both constituency and regional inputs to calculate.

Methodology

How our seat predictions are calculated

The Additional Member System (AMS)

The Scottish Parliament uses the Additional Member System (AMS), with 73 constituency seats and 56 regional list seats, for a total of 129 MSPs. Voters cast two votes: one for a constituency candidate and one for a regional party list.

Constituency Seats (73, FPTP)

Each constituency elects one MSP via first-past-the-post: the candidate with the most votes wins. Our calculator applies uniform swing to 2021 results to project outcomes.

Regional List Seats (56, D'Hondt)

Scotland is divided into 8 regions, each electing 7 regional MSPs. Only regional list votes are used for these seats.

D'Hondt Formula:

Score = Regional List Votes / (Constituency Seats Won + Regional Seats Already Won + 1)

How it works:

  1. Count constituency seats per party in each region.
  2. Allocate 7 regional seats per region in rounds:
    • Calculate each party's D'Hondt score.
    • Award the seat to the highest score.
    • Increase that party's divisor, reducing chances of winning more seats.

The divisor includes constituency wins, which compensates for parties dominating local seats, making the overall result more proportional.

Example: Glasgow Region, 2021

  • SNP won all 9 constituency seats, 34% of regional votes.
  • Labour won 0 constituencies, 25% of regional votes.
  • Conservatives: 0 seats, 20% votes; Greens: 0 seats, 12% votes.

Round 1 D'Hondt Scores:

  • SNP: 34 ÷ (9+0+1) = 3.4%
  • Labour: 25 ÷ (0+0+1) = 25% ← Wins first regional seat
  • Conservative: 20%
  • Green: 12%

Despite SNP having the highest regional vote, their dominance in constituency seats reduces their regional score, allowing smaller parties to gain seats.

2021 Outcome: SNP won 62 constituency seats but only 1 regional seat, showing how AMS balances proportionality with local representation.

Baseline Data

Projections use 2021 Holyrood election results for both constituency and regional votes.

Assumptions & Limitations

  • Uniform swing assumes national trends apply evenly.
  • Does not account for local factors, tactical voting, or candidate popularity.
  • D'Hondt assumes regional list votes match input percentages.