Single Transferable Vote Explained: How STV Works, Step by Step

Under the single transferable vote, you rank candidates in order and your vote moves on if it is not needed or cannot help. Here is how an STV count works, a simple example, and where the system is used.

Updated 9 November 2026 · 5 min read · Non-partisan explainer

Single Transferable Vote Explained: How STV Works, Step by Step — Photo: ulleo / Pixabay

The single transferable vote (STV) is a proportional voting system in which several representatives are elected for each constituency and voters rank individual candidates in order of preference: 1, 2, 3 and so on. A candidate who reaches a set number of votes, the quota, is elected. Votes a winner does not need, and votes for candidates who are knocked out, transfer to the voter's next choice. The count continues until every seat is filled.

The name describes the idea: each voter has a single vote, but it can transfer from one candidate to another so that as few votes as possible are wasted.

How STV works, step by step

Voters rank candidates. You write 1 next to your favourite, 2 next to your second choice, and so on. How many candidates you must rank depends on the rules of each system.
The quota is set. Once the valid votes are known, the count works out how many votes guarantee a seat.
First preferences are counted. Each ballot goes to the voter's first choice. Anyone who reaches the quota is elected.
Surpluses are transferred. If a winner has more votes than the quota, the extra votes pass to the next preferences shown on that candidate's ballots.
The lowest candidate is eliminated. If no one reaches the quota and seats remain, the candidate with the fewest votes is excluded and their ballots move to each voter's next available choice.
Repeat. Transfers and eliminations continue until all seats are filled, or until the number of candidates left equals the number of seats left.

The Droop quota

Almost all STV elections use the Droop quota. The usual formula is:

quota = (valid votes ÷ (seats + 1)), rounded down, + 1

The logic is that, in a contest for three seats, no more than three candidates can each reach a quarter of the votes plus one. A candidate who reaches the quota is therefore certain to be elected, and the quota is as low as it can be while still guaranteeing that. With 100 valid votes and three seats, the quota is 26. Ireland and Malta have used Droop's original formula for about a century; some modern counts use the exact figure without the "+ 1" because they transfer votes in fractions.

How surplus votes are transferred

Suppose a winner has 400 votes and the quota is 300. The 100 surplus votes should go to the second preferences, but which 100 ballots? Systems answer this differently:

Fractional transfer. All of the winner's ballots are passed on, each at a reduced value. In the example each ballot would be worth a quarter of a vote (100 ÷ 400). This is the Gregory method, used in Hare–Clark elections in Tasmania and the Australian Capital Territory, and it involves no chance.
Whole-vote transfer. In Ireland and Malta, surpluses are transferred as whole ballots, which introduces a small element of randomness into which papers move.

A worked example

A constituency elects three members. There are 1,000 valid votes and five candidates. Ann and Ben stand for the same party. The quota is (1,000 ÷ 4) rounded down + 1 = 251.

Candidate	Stage 1: first preferences	Stage 2: Ann's surplus transferred	Stage 3: Eve eliminated
Ann	502 (elected)	251	251
Ben	60	210 (+150)	224 (+14)
Cara	200	250 (+50)	270 (+20, elected)
Dev	140	170 (+30)	245 (+75)
Eve	98	119 (+21)	eliminated
No further preference	0	0	10

Stage 1. Ann has 502 first preferences, well above the quota of 251, and is elected with a surplus of 251.

Stage 2. Ann's surplus is exactly half her vote, so with fractional transfer every one of her ballots moves on at half its value. Of her 502 voters, 300 put Ben second, 100 put Cara, 60 put Dev and 42 put Eve. Halved, that gives Ben 150, Cara 50, Dev 30 and Eve 21. Cara is now one vote short of the quota. Nobody else is elected.

Stage 3. Eve has the fewest votes and is eliminated. Her votes pass to the next preferences: 75 to Dev, 20 to Cara and 14 to Ben. Ten of her voters ranked nobody else, so those votes are exhausted. Cara passes the quota and is elected.

Result. One seat remains, with Dev on 245 and Ben on 224. Cara's surplus of 19 is too small for Ben to overtake Dev, so Ben is excluded and Dev takes the final seat. Ann, Cara and Dev are elected.

Two points stand out. Ben received only 60 first preferences but stayed in contention because Ann's voters liked him too; that is how STV lets a party's supporters spread their votes across its candidates. And ten votes ended up exhausted because those voters ranked only one or two candidates, which shows why ranking more candidates gives your vote more chances to count.

Where STV is used

Republic of Ireland. The Dáil is elected by STV in constituencies of three to five members. STV is also used for European and local elections. Presidential elections and Dáil by-elections use the single-seat version, which is the alternative vote.
Malta. The House of Representatives has 65 members elected in 13 five-seat divisions by STV, and STV is also used for local councils and European elections.
Northern Ireland Assembly. The 90 members are elected by STV from 18 constituencies of five members each, a pattern in place since the March 2017 election. Before that there were 108 members, six per constituency.
Scottish local councils. The 2007 local elections, under the Local Governance (Scotland) Act 2004, were the first local government elections in Great Britain to use STV.
Australia. The Senate uses STV, with each state forming one multi-member electorate. Tasmania and the Australian Capital Territory use the Hare–Clark form of STV.

Arguments for and against

In favour

Fewer wasted votes: most voters help elect someone they ranked.
Seat shares roughly follow vote shares, and any substantial group within a constituency can expect to win at least one seat.
Voters choose between individual candidates, including candidates of the same party, rather than accepting a party's list.
No single party can take every seat in a constituency unless the constituency is very small.

Against

The count is more involved than a simple tally, and the transfer rules can be hard to explain.
Ballots can become exhausted when voters rank only a few candidates, so not every vote counts to the end.
Voters can still vote tactically, and some find a long ranked ballot confusing.
Multi-member constituencies are larger than single-member ones, so the link between one representative and one area is looser, and candidates from the same party compete with each other for preferences.

How STV compares with list-based systems is covered in how proportional representation works.

Common questions

How is the STV quota calculated?

Most STV elections use the Droop quota: divide the valid votes by the number of seats plus one, round down and add one. In a three-seat contest with 1,000 votes, the quota is 251.

Do I have to rank every candidate under STV?

That depends on the rules where you vote. Where you may stop early, your vote cannot transfer any further once every candidate you ranked has been elected or eliminated.

Is STV the same as the alternative vote?

The alternative vote is the single-seat version of the same idea. STV elects several members per constituency using a quota, which makes it proportional; the alternative vote elects one.

Where is STV used in the UK?

Its uses include elections to the Northern Ireland Assembly and local council elections in Scotland, which first used STV in 2007. The House of Commons uses first past the post.