At a $1 unit, a full trifecta box costs $60 for 5 horses, $120 for 6, $210 for 7 and $336 for 8. The formula is runners x (runners minus 1) x (runners minus 2), so the cost climbs fast. A flexi bet lets you set a smaller outlay and collect a matching percentage of the dividend.
Full box costs at a $1 unit
Each combination is one line on your ticket, and each line costs your unit. The table shows the full cost of each box, with an example flexi outlay and the percentage it holds. The cost grows more than fivefold between 5 and 8 horses.
| Horses boxed | Combinations | Full cost at $1 | Example flexi outlay |
|---|---|---|---|
| 5 | 60 | $60 | $30 (50%) |
| 6 | 120 | $120 | $40 (33.33%) |
| 7 | 210 | $210 | $50 (23.81%) |
| 8 | 336 | $336 | $50 (14.88%) |
Source: Calculated at a $1 unit, combinations = runners x (runners minus 1) x (runners minus 2), as at November 2026.
The NSW Totalizator Rules list a racing unit of 50 cents. Halve the unit to 50 cents, where the operator offers it, and the costs halve too.
How flexi brings the outlay down
Divide your outlay by the combinations to get your percentage, then expect that share of the dividend if the box hits. If an 8-horse box pays $1,000 for a $1 unit, the 14.88% ticket collects about $148.81. Check the minimum outlay with your operator, because it varies.
What each extra horse adds
Going from 5 to 6 horses adds $60, from 6 to 7 adds $90 and from 7 to 8 adds $126. The eighth horse alone costs more than a whole 5-horse box. Flexi trims the stake but not the ratio: a 14.88% ticket costs 14.88% of the box and pays 14.88% of the dividend. If you need eight runners to feel comfortable, the race may be too open to box at all. The basics are in how much a boxed trifecta costs.
Frequently Asked Questions
How many combinations are in a 9-horse trifecta box?
504, which is 9 x 8 x 7. At a $1 unit that is $504 for a full ticket.
Does flexi change the odds of winning?
No. You hold the same combinations and take a smaller share of the dividend. Spending less per line does not make the box harder to hit.
Is the maths the same for a First Four box?
No, because four positions are filled. A 5-horse First Four box is 120 combinations and a 6-horse box is 360.
Horse racing betting involves financial risk. Bet only what you can afford to lose. For support, visit Gambling Help Online or call 1800 858 858.