When people talk about ranked choice voting, what they usually mean — mechanically — is instant-runoff voting (IRV). IRV is the algorithm: a series of elimination rounds in which the last-place option is removed and its votes passed on to each voter's next preference, repeated until one option holds a clear majority. It is called 'instant' runoff because all rounds are calculated from one set of ranked ballots, eliminating the need for a separate follow-up election. Chooseday implements IRV automatically whenever ranked choice mode is selected.
Instant-runoff voting — definition
Instant-runoff voting (IRV) is a preferential voting algorithm in which voters rank the available options from most preferred to least preferred, and a winner is determined through successive elimination rounds. In each round, all active votes are counted based on the highest-ranked option still in the race on each ballot. If any option holds more than 50% of active votes, it is declared the winner. If not, the option with the fewest votes is eliminated, and those ballots are transferred to each voter's next preference. The process repeats until one option achieves a majority. IRV is widely used in political elections in Australia, Ireland, and several US jurisdictions, and is the standard algorithm in team decision tools that offer ranked choice voting.
The IRV algorithm — step by step
Voters rank all options
Each participant ranks every option in order of preference (1st, 2nd, 3rd, etc.). Voters may stop before ranking all options, but any ballot that exhausts its rankings is simply removed from subsequent rounds — it does not affect the other active votes.
Count first-preference votes
Tally all ballots by their current top-ranked active option. This gives the first-round vote share for each option. If any option already holds more than 50% of first-preference votes, it wins immediately — no further rounds are needed.
Eliminate the last-place option
The option with the fewest first-preference votes in this round is removed from the ballot. All voters who had that option as their current top choice have their vote transferred to their next-ranked option that is still in the race.
This redistribution is the core innovation of IRV: no vote is discarded. A voter's support for a long-shot option does not prevent their preference from counting when that option is eliminated.
Recount and repeat
After redistribution, recount all active ballots based on each ballot's new top-ranked option. Check again for a majority winner. If found, the process ends. If not, eliminate the new last-place option and redistribute again. Continue until one option holds a majority.
Worked example of instant-runoff voting
A team of 10 votes on four options — A, B, C, D — for a new product name. Round 1 results: A=4, B=3, C=2, D=1. No option exceeds 5 (50%), so D is eliminated. D's single ballot had C as the second choice, so C now has 3 votes. Round 2: A=4, B=3, C=3. Still no majority. C is eliminated (tied with B; C is eliminated by tiebreak rule). The two C ballots had B and A as second choices — one each. Round 3: A=5, B=4. A has exactly 50% but the threshold is more than 50%, so with one more redistribution or by threshold rules defined in advance, A wins. In practice, Chooseday resolves these edge cases automatically and displays the full round-by-round breakdown to all participants.
When to use instant-runoff voting
IRV is the right choice when you have four or more options and want to avoid vote splitting — the failure mode where similar options divide support and a minority favourite wins. It is especially valuable for high-stakes decisions where team buy-in matters: because every voter's full preference is considered, people accept IRV results more readily than plurality results, even when their first choice does not win. For simple two-option decisions, or when speed is the priority, standard majority voting is simpler and sufficient. Chooseday runs IRV automatically in ranked choice mode — you never have to calculate redistribution rounds manually.
Frequently asked questions
Instant-runoff voting (IRV) is a voting algorithm in which voters rank options in order of preference, and the winner is determined through a series of elimination rounds. In each round, the option with the fewest first-preference votes is eliminated and those votes are redistributed to the next-ranked option on each ballot. Rounds continue until one option holds a majority of the active votes. IRV is called "instant" runoff because all these rounds are calculated from a single set of ballots, with no need for a separate physical runoff election.
Ranked choice voting (RCV) is the broader method — it describes any voting system in which voters rank options by preference. Instant-runoff voting is the specific counting algorithm most commonly used to determine the winner in a ranked choice election. In practice, the terms are often used interchangeably, but IRV is the precise mechanism: last-place elimination followed by vote redistribution, repeated until a majority winner emerges.
Step 1: count all first-preference votes. Step 2: if any option has more than 50% of active votes, that option wins. Step 3: if not, eliminate the option with the fewest first-preference votes. Step 4: redistribute each eliminated ballot to the next-ranked option still in the race. Step 5: repeat from Step 2 until a majority winner is found. If all remaining ballots exhaust their rankings simultaneously, the option with the most votes at that point wins.
Use instant-runoff voting when you have four or more options and want to avoid the vote-splitting problem of plurality voting, when you need a winner with genuine majority support rather than just the most first-place votes, or when you want team members to express nuanced preferences without strategically voting for a lesser favourite. For two or three clearly distinct options, standard majority voting is simpler and equally valid.