How Pari-Mutuel Dividends Are Calculated: Pools, Deductions and Rounding

How pari-mutuel payouts are calculated

Pari-mutuel betting works backwards from most betting you may have seen. With fixed odds, the price is agreed when you place the bet and that is what you get paid. With pari-mutuel, or tote, betting, nobody knows the final price until the pool closes. The dividend is a result of the betting, not a prediction of it.

The sequence is always the same. Bets come in and are added to a pool for that bet type. When betting closes, the operator takes its deduction from the pool. The remainder, called the net pool, is divided by the number of unit bets on the winning combination. That gives the dividend per unit, which is then rounded and declared.

On Japanese horse racing, payouts are shown as the amount paid for a JPY 100 bet, which makes the numbers easy to read at a glance¹. If you want the total returned on your own ticket, you multiply the declared payout by your purchase amount⁷.

The practical consequence is that the odds you see during the day are estimates. They are recalculated continuously as money arrives, and they can move a long way between the first race and the last.

The pool: how bets are combined

Every bet type has its own pool. Win bets go into one pool, place bets into another, and so on. Money on one bet type does not affect the dividend on another.

Within a pool, all stakes are pooled together regardless of who placed them. A JPY 100 bet and a JPY 10,000 bet on the same combination sit in the same pool, and both are paid at the same rate per unit. What differs is only how many units each bettor holds.

This is why the size of the pool matters as much as the result. A small pool with a lot of money on one combination produces a short dividend. A large pool with money spread widely produces longer ones. At Kasamatsu Keiba, the operator explains it plainly: the payout rises or falls depending on how many people bought a given horse or bracket and how much they put on, so the odds change moment to moment and are calculated by computer and displayed on the in-venue screens and odds boards⁸.

Football works the same way where pari-mutuel betting is offered. Dividends are declared to the unit bet or partial unit bet for each pari-mutuel bet type, so the structure is identical even though the sport is different⁹.

Deductions: what comes out before payouts

The deduction is the operator's share, and it comes out before any winning ticket is paid. What is left is the net pool.

The rates differ by operator and by bet type, and they are published. On Hong Kong pools, the Six Up pays out 50 percent of the net pool to the winning combination and 50 percent to the Six Win Bonus, with 2 percent of the pool deducted as an Operator Reserve Deduction from the operator's revenue³. The published rates for the other Hong Kong pools are:

• The Forecast pool pays 80.5 percent³
• The Trio pool pays 77 percent³
• The Tierce, First 4, Quartet and Treble pools pay 75 percent³

Outbound commingled pools on designated simulcast races from France pay 84.95 percent, subject to the rate announced by France PMU from time to time³.

Japanese horse racing sits in a similar band. Research on the Japanese market puts the refund total at 70 to 80 percent of sales proceeds under the pari-mutuel method, and the loss arises at the point the ticket is bought rather than at the point the race is run². Broken down by bet type, win and place bets have returned 80.0 percent and WIN5 bets 70.0 percent².

Keirin's wide bet pays 75 percent of relevant sales¹⁰. The wide bet formula published by keirin is worth reading closely because it shows the whole mechanism in one line: sales on the combination you want plus total sales on non-winning combinations, multiplied by 75, divided by the number of tickets on the combination you want, equals the payout for that combination¹⁰.

The deduction is not a fee charged to you separately. It is already gone by the time the dividend is declared, which is why the dividend looks lower than a simple division of the pool would suggest.

Dividing the net pool among winning tickets

Once you have the net pool, you divide it by the number of unit bets on the winning combination. That is the dividend per unit.

Some bet types split the net pool before dividing. In Hong Kong, Double Betting and Treble Betting divide 85 percent of the net pool by the unit bets on the winning combination and the remaining 15 percent by the unit bets on the consolation combination⁴. Triple Trio works the same way, 85 percent to the winning combination and 15 percent to the consolation⁴. The Chinese-language rules for the same bet types state the split identically, 85 percent and 15 percent¹¹.

Place betting with two dividends works differently again. The net pool is divided into as many parts as there are winning combinations backed, and each part is then divided by the units bet on that combination¹¹. In a dead heat, the same principle applies: the net pool is subdivided into as many parts as there are winning combinations that have been backed⁴.

Where the total winning investment on a combination is less than a full unit bet, the dividend is declared to the minimum partial unit bet and paid by reference to that¹². Partial unit bets receive the proportion of the announced dividend that they bear to a full unit, and the unpaid balance is credited to the jackpot pool¹².

There is also a floor in some markets. On Hong Kong commingled pools, the dividend declared for a combination win and place bet cannot be less than the betting unit plus ten cents¹¹.

Odds as payout multiples: the KEIRIN example

Keirin publishes its odds as payout multiples, and the operator is explicit that these are important information because they indicate the payout amount for a winning wager¹³. The lower the multiple, the more popular the pick; the higher the multiple, the less popular¹³.

The arithmetic is simple multiplication. A JPY 100 ticket at odds of 4.5 pays JPY 450 if it wins¹⁴. The same example appears in the Chinese-language guidance, where a JPY 100 ticket at 4.5 returns JPY 450¹⁵, and in the Korean-language guidance with the same figures⁵. The 4.5 in that example is the price for rider 1 finishing first and rider 7 second¹⁶.

At the other end of the board, the numbers get large. A JPY 100 two-car win bet on first place number 2 and second place number 3, at odds of 9418.5, returns JPY 941,850¹⁴. The same figure appears for first place number 6 and second place number 8¹⁴. A JPY 100 bet on 1-7 at 4.5 returns JPY 450¹⁴.

Japanese horse racing uses the same presentation. The odds for horse number 2 at 1.9 mean a JPY 100 bet pays out JPY 190¹. At Kasamatsu Keiba, a quinella on 3-6 at 21.4 means a JPY 100 stake becomes JPY 2,140⁸.

Stake: JPY 100

Favorites and outsiders: what the odds tell you

Because the dividend is a direct function of how much money sits on each combination, the odds board is a popularity chart as much as a price list. Keirin states it directly: the lower the odds, the more popular the pick, and the higher the odds, the less popular¹⁶. The lowest number on the board indicates the race favorite¹³.

This is a useful thing to understand before you read a tote board for the first time. A short price does not mean the operator thinks a result is likely. It means a lot of money has already gone onto that combination, so each winning unit has to share the net pool with more units. A long price means the opposite: few units are on it, so each one takes a bigger slice.

The same logic explains why prices move during the day. At Kasamatsu Keiba, the operator notes that the payout changes depending on how many people buy a given horse or bracket and by how much, so the odds change from moment to moment⁸. If you are comparing a pari-mutuel price with a fixed odds price elsewhere, remember that only one of them is a promise. The other is a running estimate.

Merged pools and consolation or bonus combinations

Some bet types combine pools, and some reserve part of the net pool for a second set of combinations.

The Six Up is a good example. Fifty percent of the net pool is divided by the unit bets selecting the winning combination, and 50 percent goes to the Six Win Bonus⁴. The jackpot for Six Up is allocated to and aggregated with that 50 percent for dividend calculation⁴.

Consolation combinations appear across several bet types. Double Betting and Treble Betting reserve 15 percent of the net pool for the consolation combination⁴. Triple Trio does the same⁴. The Chinese-language rules for the Double and Treble bets state the split as 85 percent to the winning combination and 15 percent to the consolation combination¹¹.

Where a winning or consolation combination has no bets at all, the relevant net pool is transferred to the jackpot pool rather than being paid out¹. The jackpot then accumulates, and an amount decided as a jackpot is deducted from the jackpot pool and transferred into the net pool of the same type of football betting designated by the operator¹.

Merged pools also have minimum field requirements. A Quartet and First 4 merged pool closes if there are fewer than 6 starters, and all bets are refunded⁴. Single race pools have their own thresholds: a Win pool closes with fewer than 2 starters, and a Place pool with two dividends closes with fewer than 4 starters, with all bets refunded in each case⁴.

What the operator can change: bet types and declared dividends

The operator decides which bet types to offer, and it can change that menu. Hong Kong's rules state that the operator may decide from time to time to offer the types of pari-mutuel bets in relation to any race or races⁴, and the same discretion applies to pari-mutuel football bet types on a nominated match or matches⁹. For outbound commingled bets, the operator may decide the types offered, the unit bet or partial unit bet or minimum flexi bet unit stake, and which pari-mutuel bet types flexi bet is available on¹⁷.

Dividends are declared to a unit bet, and that is the basis on which everyone is paid. Where a partial unit bet is involved, it is paid the part of the dividend it bears to the unit bet, and the unpaid balance is credited to the jackpot pool¹².

Once payment has started, the result is treated as settled for payment purposes. Once the operator has started paying out dividends or refunds based on a referee's declaration, any later amendment to that declaration is ignored for payment purposes⁹.

Errors can be corrected. The operator may revise a payout found to contain an error or miscalculation after publication; holders who have not yet claimed receive the revised payout, and holders who have already claimed may claim the difference¹⁸. The operator also reserves the right to rectify an erroneous dividend, refund or early settlement payment by debiting or crediting the relevant betting accounts¹⁹.

Operators can also set limits. The operator may set maximum or minimum unit bet amounts, total bet amounts and maximum payout per ticket, per bet, per bet type and per betting day, and may amend them without notice¹⁸.

If a race is void, the money comes back. Where none or only one of the horses due to run remains, or the race does not take place, betting is null and void, and holders of tickets in the nullified race may claim face-value refunds⁶. On the football side, if a match is called off, the odds for the affected match are set to one, and if all matches are called off the bets are void and refunded²⁰.