How multi bet odds are calculated, why the bookmaker’s margin compounds with every leg, how same-game multis are priced for correlation, and how void legs settle.
Multi Bets and Same-Game Multis Explained: Why the Margin Compounds
A multi bet — a parlay or accumulator everywhere else — rolls several selections into one bet. Every leg has to win for it to pay, and in return the prices multiply together, which is how three or four modest selections turn into a payout worth more than a hundred dollars on a twenty-dollar stake.
The multiplying works both ways, and that is the part the advertising leaves out. A bookmaker’s margin sits inside every price, so it compounds with each leg you add. This guide shows the arithmetic behind multi bet odds, what that compounding actually costs, how same-game multis are priced differently, how void and postponed legs settle, and where multis sit under New Zealand’s betting rules.
What this article answers: How multi bet odds are worked out, why the bookmaker’s margin compounds with every leg you add, how a same-game multi is priced differently, and what happens when a leg is void.
Main points
- Multi odds are simply the legs multiplied together: 1.85 x 2.10 x 1.60 = 6.22.
- Every leg has to win. One losing leg and the whole bet pays nothing.
- The margin compounds. A true 50-50 priced at 1.90 costs 5% of fair value over one leg and about 18.6% over four.
- A same-game multi is priced for correlation, so it almost always pays less than the same legs multiplied out.
- A void leg drops out and the multi re-prices on the legs that remain; a dead heat halves that leg’s price.
6.22Combined price of legs at 1.85, 2.10 and 1.60
16.1%Implied chance that three-leg multi lands
18.6%Value lost to margin on four legs priced at 1.90
18+Minimum age to bet in New Zealand
What a multi bet actually is
A multi is a single bet made up of two or more selections, called legs. The stake goes on once, and the bet only pays if every leg comes in. Lose one and the whole thing is gone, no matter how comfortable the other legs were.
In exchange, the returns are calculated by multiplying the legs rather than adding them. That is why multis look so attractive on a small stake: a modest three-leg combination can pay more than six times the outlay, and eight legs of near-favourites can pay more than a hundred times. The legs can come from different sports and different days, and most operators let you mix codes freely.
The trade-off is that you are betting on an intersection of events rather than a single one. Three selections each with a 55% chance of winning are not a 55% bet. They are a 16.6% bet, because all three have to land.
How multi bet odds are calculated
Decimal odds make this easy, because a decimal price already includes your stake. Multiply the legs and you have the multi price:
Multi price = leg 1 x leg 2 x leg 3 …
Legs at 1.85, 2.10 and 1.60 give 1.85 x 2.10 x 1.60 = 6.22. A $20 stake returns $124.32, a profit of $104.32. The implied chance is one divided by the price, so 1 / 6.22 = 16.1%. Our betting odds explained guide covers converting between decimal, fractional and implied chance.
The table below takes the simplest possible case: a genuine coin flip, which is worth 2.00, offered at the usual 1.90. Watch what happens to the share of fair value you keep as legs are added.
| Legs at 1.90 | Multi price | Implied chance | Fair price at 2.00 a leg | Share of fair value kept |
|---|---|---|---|---|
| 1 | 1.90 | 52.6% | 2.00 | 95.0% |
| 2 | 3.61 | 27.7% | 4.00 | 90.3% |
| 3 | 6.86 | 14.6% | 8.00 | 85.7% |
| 4 | 13.03 | 7.7% | 16.00 | 81.5% |
| 6 | 47.05 | 2.1% | 64.00 | 73.5% |
| 8 | 169.84 | 0.6% | 256.00 | 66.3% |
Why the margin compounds
Every price a bookmaker posts is shaded in its favour. On a two-way market at 1.90 and 1.90, the implied chances add up to 105.3% rather than 100%, and that extra 5.3% is the overround. Expressed as a share of turnover it is a margin of about 5%.
On a single bet you pay that margin once. On a multi you pay it on every leg, because the shaded prices are multiplied by each other. Four legs at 1.90 pay 13.03 where a fair market would pay 16.00 — you keep 81.5% of the value, so 18.5% has gone. By eight legs you are keeping about two thirds.
This is the single most useful thing to understand about multis. The bet is not bad because the odds are long; it is expensive because the house edge is applied repeatedly. Adding a fifth leg because it “only” needs to be a near certainty still adds another slice of margin.
A worked three-leg example
Take the three legs from earlier at 1.85, 2.10 and 1.60, with a $20 stake.
| Line | Figure |
|---|---|
| Multi price | 6.22 |
| Stake | $20.00 |
| Return if every leg wins | $124.32 |
| Profit | $104.32 |
| Implied chance | 16.1% |
| Same legs at fair prices | about 7.20 |
| Return at fair prices | about $143.90 |
Nothing about that makes the bet unwinnable. It simply means that a three-leg multi has to beat a stiffer price than three separate singles would.
The calculator below multiplies your legs, marks the ones that have lost or been voided, and shows how the margin compounds across the legs that are still live.
Multi bet calculator
Add your legs, mark any that lost or were voided, and see the combined price, the return and the compounded margin
Stake ($)
Assumed margin per leg (%)
| Leg | Decimal odds | Status | Remove |
|---|
Combined odds—
Return if it lands—
Profit—
Implied chance—
Compounded margin—
Educational tool from Sports-Betting.nz. Results are estimates — the bet slip or official dividend always decides. 18+ only. Free, confidential help: Gambling Helpline 0800 654 655 or text 8006.
Same-game multis and why they price differently
A same-game multi, or SGM, combines several selections from one match: the winner, the first try-scorer, a total, a player’s disposal count. Standard multi arithmetic assumes the legs are independent, and inside a single game they plainly are not. If a team wins comfortably, its outside backs are far more likely to have crossed, and the match total is more likely to be high.
Operators therefore price SGMs with a correlation model rather than by multiplying. When the legs support each other, the model produces a shorter price than the raw multiplication would, because the combination is more likely than independence implies. When the legs pull against each other, the price can be longer.
Two practical consequences follow. First, you cannot check an SGM price by multiplying the singles — the number you get will usually be bigger than the price offered, and that gap is not necessarily margin. Second, correlation modelling is harder than pricing a head-to-head, and the margin loaded into SGMs is generally wider than on a standard multi. Treat them as the most expensive product on the board.
Finals football is where SGMs get the heaviest promotion. If you are looking at the 2026 NRL finals, the same caution applies to every “boosted” multi in the app: the boost is applied to a price that already carries a compounded margin.
Checking the margin in a market yourself
You cannot see a bookmaker’s margin on a single price, but you can see it across a whole market. Add up the implied chances of every outcome; anything above 100% is the overround. The calculator below does it for two-way markets, three-way markets with the draw, and full racing fields.
Market margin calculator
Enter every price in a market to see the overround, the margin and what each price would be with the margin removed
Market type
| Outcome | Odds | Fair odds | Fair chance | Remove |
|---|
Market adds up to—
Overround—
Bookmaker margin—
Educational tool from Sports-Betting.nz. Results are estimates — the bet slip or official dividend always decides. 18+ only. Free, confidential help: Gambling Helpline 0800 654 655 or text 8006.
Run the two-way default and you will see 105.3% and a margin of 5.0%. That is the number that gets multiplied every time you add a leg. Racing fields and novelty markets often sit far higher, which is why multis built from exotic legs are the dearest of all.
Void legs, postponements and dead heats
- Void or scratched leg. The leg drops out at 1.00 and the multi is settled on the legs that remain. A five-leg multi with one scratching becomes a four-leg multi at a shorter price, not a loser.
- Postponed or abandoned match. Rules vary by operator and sport. Most void the leg if the match is not completed within a stated window, but some hold the bet open for days. This is worth reading before finals week, not during it.
- Dead heat. The affected leg’s price is halved for a two-way dead heat before the multiplication, which cuts the whole multi roughly in half.
- Cash out. An offer to close a live multi early is priced with the operator’s margin taken again, on top of the margin already in every leg.
When a multi makes sense, and when it does not
A multi is a staking decision, not a betting edge. You are trading a high chance of a small return for a low chance of a large one, and paying for the privilege each time you add a leg.
- Defensible: two or three legs you would happily back as singles, on a stake you would be comfortable losing. The compounded margin on three legs is real but modest.
- Poor value: six or eight legs assembled to reach a target payout. You are giving up a quarter to a third of the fair price, and the chance of every leg landing is usually in low single figures.
- Worth pausing on: promoted multis and boosts. Work out the plain price first, then see what the boost is actually worth against it.
If you want the long-shot payout without the compounding, the alternative is a single bet at a long price. It is one margin instead of six, and the arithmetic is much easier to check. Our betting lines and handicaps guide covers the other place the same trade-off shows up, and the each-way betting guide covers splitting a stake across two outcomes instead of stacking legs.
Multis and the New Zealand rules
Since 28 June 2025, TAB NZ has been the only operator allowed to offer online racing and sports betting to people in New Zealand, so a multi placed legally here is a TAB NZ multi. Offshore apps promoting multis to New Zealand residents are operating outside that rule, and money placed with them sits outside the protections and the account tools that come with a licensed operator. Our TAB NZ overview covers deposit limits, time-outs and self-exclusion.
Whatever you use, the practical safeguard is a limit set before finals week rather than during it. Multis are designed to feel cheap, and a run of $10 multis adds up faster than most people track.
Please read: This page is general betting information for readers aged 18 and over. It is not betting, financial or legal advice, and it does not encourage anyone to gamble. Since 28 June 2025, TAB NZ has been the only operator allowed to offer online racing and sports betting to people in New Zealand.
If gambling is causing problems for you or someone close to you, free and confidential help is available 24/7 from the Gambling Helpline on 0800 654 655 or free text 8006. The Problem Gambling Foundation also offers free counselling.
Reference sources
FAQs
How are multi bet odds calculated?
Multiply the decimal price of every leg. Legs at 1.85, 2.10 and 1.60 give a multi price of 6.22, so a $20 stake returns $124.32 if all three win.
Why are multi bets considered poor value?
Because the bookmaker’s margin is inside every leg and the legs are multiplied. A coin flip priced at 1.90 instead of 2.00 costs you 5% of fair value once, but about 18.6% across four legs and a third across eight.
What is a same-game multi?
Several selections from one match combined into a single bet. Because the legs are related, they are priced with a correlation model rather than by straight multiplication, and the margin is usually wider than on a standard multi.
What happens if one leg of my multi is void?
The void leg drops out and the bet is settled on the remaining legs at a correspondingly shorter price. A five-leg multi with one scratching pays as a four-leg multi.
How many legs can a multi have?
Operators set their own maximum, usually somewhere between ten and twenty selections. The calculator on this page handles up to twelve, which is well past the point where the compounded margin dominates the bet.
Can I bet multis legally in New Zealand?
Yes, through TAB NZ, which since 28 June 2025 has been the only operator permitted to offer online racing and sports betting to people in New Zealand.
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