Ranked-Choice Voting Explained: IRV and STV with Examples

Ranked-choice voting lets voters rank candidates in order of preference: 1 for their favourite, 2 for their next choice, and so on. If no one wins outright, the lowest-ranked candidates are eliminated and their ballots are transferred to the next preference, until a winner emerges. For a single seat this is called instant-runoff voting (IRV); for several seats the usual form is the single transferable vote (STV).

The appeal is simple: one ballot does the work of several runoff rounds, and voters can support a less-known candidate without fearing that their vote is wasted.

How instant-runoff voting works

1. Count everyone’s first preferences.
2. If a candidate has more than half of the valid ballots still in play, they win.
3. If not, eliminate the candidate with the fewest votes.
4. Move each of that candidate’s ballots to the next preference that is still in the race.
5. Repeat from step 2.

Worked example (IRV, one seat)

Invented example for illustration. A club elects its chair. 100 members vote. Three candidates stand: Amber, Birch and Cedar.

Round	Amber	Birch	Cedar	Action
1 (first preferences)	42	33	25	No one over 50; Cedar eliminated
2 (after transfer)	42 + 6 = 48	33 + 19 = 52	out	Birch wins

Of Cedar’s 25 ballots, 19 listed Birch as second choice and 6 listed Amber. Under a plain ‘most votes wins’ rule, Amber would have won with 42 per cent. Under IRV, Birch wins because a majority of the voters preferred Birch to Amber once Cedar was out. That is exactly the effect the method is designed for.

How the single transferable vote works

STV is used when several seats are filled at once, for example a board of five. It needs a quota: the number of votes that guarantees a seat. The most common is the Droop quota:

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

The count then runs like this:

1. Any candidate whose first preferences reach the quota is elected.
2. Their surplus (votes above the quota) is transferred to the next preferences, at a reduced value so that no voter counts twice.
3. If no one reaches the quota, the lowest candidate is eliminated and their ballots are transferred at full value.
4. This continues until all seats are filled.

Short example (STV, two seats)

Invented example. 90 valid votes, two seats. Quota = (90 ÷ 3) + 1 = 31. Dana gets 40 first preferences and is elected with a surplus of 9. Those 9 votes’ worth of ballots move to their second preferences, mostly to Eli, who then passes 31 and takes the second seat. Different counting rules (Gregory, Meek and others) handle the fractions differently, which is why organisations should name the exact rule or let tested software do the arithmetic.

Where ranked ballots are used

• Ireland: STV for elections to the Dáil and local councils; the presidential election uses a ranked single-seat count.
• Malta: STV for parliamentary elections.
• Scotland and Northern Ireland: STV for local elections; Northern Ireland also for its Assembly.
• Australia: preferential voting for the House of Representatives.
• United Kingdom: in a 2011 referendum, voters rejected switching Westminster elections to the Alternative Vote, a form of IRV.

Many professional bodies, student unions and associations also use STV for committee elections.

Pros and cons

Advantages	Drawbacks
No separate runoff round needed	Counting is more complex and harder to check by hand
Fewer ‘wasted’ votes and less tactical voting	Voters need a short explanation of the ballot
Winners usually have broader support	Results can shift in non-obvious ways between rounds
STV gives proportional results in multi-seat elections	Exhausted ballots can reduce the final majority

Should your group use it?

Ranked voting makes most sense when you have three or more candidates for one post, or when you fill several seats and want minorities to be represented fairly. For a simple yes/no motion it adds nothing. If you want a method that is even easier to explain, look at approval and score voting.

Practical tips:

• Fix in your election rules which method (IRV or STV), which quota and which transfer rule you use.
• Decide what counts as a valid ballot (for example, duplicate rankings).
• Publish the round-by-round results so members can follow the count.
• If you vote online, choose a tool that supports your exact rule; our online voting software comparison shows which tools offer ranked ballots, and the guide to board elections online covers the rest of the process.

How majorities are defined in the first place is covered in majority and quorum.