Scottish Parliament Seat Calculator

The Scottish Parliament uses the Additional Member System (AMS). Voters cast two votes: one for a constituency candidate (first-past-the-post) and one for a regional party list.

There are 73 constituency seats and 56 regional list seats, for a total of 129 MSPs. A party needs 65 seats for a majority.

Scotland is divided into 8 regions, each electing 7 regional MSPs using the D'Hondt method. The D'Hondt formula divides each party's regional vote by the number of seats they've already won (constituency + regional + 1), which compensates for parties that dominate constituency seats and makes the overall result more proportional.

The calculator applies differential swing to baseline results. When you enter polling numbers, the model calculates how much each party's vote has changed nationally and applies that swing to each constituency, adjusted for local conditions.

Constituencies where a party is already strong see slightly different swing effects than seats where they are weak. This produces more realistic results than simple uniform swing, which assumes every seat moves by the same amount.

For the regional list, the same approach is applied to each region's vote totals, then D'Hondt allocation determines which parties win the 7 list seats per region.

The baseline is the actual result of the 7 May 2026 Holyrood election, fought on the new constituency and regional boundaries, as published by the Electoral Management Board for Scotland. Every constituency vote share, regional list total and seat count the calculator starts from is read from that result.

Constituency swings are applied to that baseline using differential swing. Regional list swings are applied half as a uniform change and half in proportion to each party's local share, then D'Hondt allocates the 7 list seats in each region. Parties that are not standing in a constituency or region are removed. If a poll does not report Others, Others is held at its 2026 share.

Reform UK stood everywhere in 2026 and has a real vote share in every constituency and region, so the calculator swings their support from that base like any other party. No proxy or estimated starting point is used.

The model does not account for local factors, tactical voting, or candidate popularity. The constituency swing multipliers that decide how much a party's swing varies between its strong and weak areas are unchanged from the 2021-era model; Reform UK has no constituency multipliers and takes a uniform swing there. The regional list method was tested against the 2026 election from the 2021 baseline. Regional list seat allocation assumes the input vote shares apply evenly across all regions.