MMP in one minute
At a general election, you cast two votes. Your party vote is the important vote for deciding each qualifying party's overall share of seats. Your electorate vote chooses one local candidate. The two votes are counted separately, so you can support a local candidate from one party and give your party vote to another.
A party normally enters the proportional allocation by winning at least 5% of party votes nationwide or by winning an electorate seat. Its electorate winners take the first places within its total entitlement; list MPs fill most of the remaining places. The result is usually a 120-seat Parliament whose party balance is close to the qualifying party-vote result.
Two votes, two different jobs
The party vote
The party vote answers: which party should have influence in Parliament? It is not a vote for a prime minister and it is not added to your electorate vote. Once the qualifying parties are known, the nationwide party-vote totals drive the proportional seat calculation.
The electorate vote
The electorate vote chooses the MP for your local electorate. The candidate with the most electorate votes wins; they do not need more than half. That contest can therefore produce a different winner from the party that leads the party vote in the same area.
This separation is deliberate. It lets voters judge a local candidate independently from their preferred party and combines local representation with a proportional Parliament.
Who qualifies for proportional seats?
A party qualifies if it wins 5% or more of the nationwide party vote or wins at least one electorate. The second route is often called the electorate-seat pathway. Once a party qualifies through either route, its party votes are included when seats are allocated.
If a party finishes below 5% and wins no electorate, it receives no list-seat entitlement. Its party votes do not move to another party, but they are excluded from the proportional allocation. That means the shares of the parties that did qualify are effectively recalculated over a smaller pool of votes.
Your electorate vote remains valid regardless of what happens to your party vote. A local candidate can win an electorate even when their party is below 5% nationwide.
How the 120 seats are allocated
New Zealand uses the modified Sainte-Laguë formula. Each qualifying party's party-vote total is divided by 1.4, then 3, 5, 7 and successive odd numbers. The resulting quotients are ranked from highest to lowest. Seats are awarded to the 120 highest quotients.
The formula sounds technical, but its purpose is straightforward: convert votes into whole seats while keeping each qualifying party's representation close to its share of the qualifying vote. The 1.4 opening divisor makes winning a first seat slightly harder than under the standard Sainte-Laguë sequence.
A simplified worked example
Assume five parties receive the following nationwide party votes, no electorate result creates an overhang, and Party E wins no electorate:
| Party | Party vote | Qualifies? | Seats |
|---|---|---|---|
| Party A | 40% | Yes | 50 |
| Party B | 32% | Yes | 40 |
| Party C | 18% | Yes | 22 |
| Party D | 6% | Yes | 8 |
| Party E | 4% | No | 0 |
Party E's 4% is outside the allocation, so the four qualifying parties divide 120 seats between them. Modified Sainte-Laguë produces 50, 40, 22 and 8 seats in this example. This is why a party crossing 5% can change the arithmetic for every other party—not just gain seats for itself.
Electorate MPs and list MPs
After each party's total seat entitlement is known, its electorate winners are counted first. List MPs then fill the gap between those electorate wins and the party's total entitlement.
For example, suppose a party is entitled to 36 seats and wins 20 electorates. Those 20 winners become electorate MPs and the next 16 places go to candidates from the party list. Electorate and list MPs have the same status when Parliament votes; the labels describe how they entered Parliament, not different levels of authority.
A party that qualifies through an electorate seat can receive additional list MPs if its party-vote share entitles it to more seats than the electorates it won.
What is an overhang?
An overhang occurs when a party wins more electorate seats than its party vote would otherwise entitle it to. The party keeps those electorate seats. Other parties do not lose seats to compensate, so Parliament temporarily grows beyond the standard 120 seats.
Imagine a party whose party vote would entitle it to six seats but whose candidates win seven electorates. It keeps all seven electorate MPs, creating a one-seat overhang and a 121-seat Parliament. Because the chamber is larger, the number of seats needed for a majority also rises.
Overhangs are uncommon but important in close elections. Any seat calculator must therefore state its electorate assumptions rather than treating party-vote percentages as the entire result.
How MMP produces a government
MMP elects Parliament; it does not automatically make the largest party the government. A government must be able to maintain the confidence of the House. If no party has enough seats alone—which is common under MMP—parties negotiate after the election.
A coalition brings parties into government together. A confidence-and-supply agreement can instead give a government reliable support on confidence votes and the money needed to govern while leaving the supporting party outside Cabinet. Other arrangements are possible, but the decisive question is whether a proposed government can command enough parliamentary support.
That is why election coverage should look beyond first place. Threshold outcomes, electorate wins and possible support partners can matter more than the gap between the two largest parties.
Apply MMP to the current race
Use the NZ Polls coalition calculator to change party-vote shares and test parliamentary majorities. The current seat estimate applies the published NZ Polls average and stated electorate assumptions; it is a mechanical estimate, not a prediction of coalition negotiations.
For the legal process and official calculations, consult the Electoral Commission's MMP overview, its explanation of how MPs are elected, and the official seat allocation calculator.