Combination Forecast Calculator: Reverse Forecast Costs in UK Racing
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Most punters place their first combination forecast without realising they have just multiplied their stake by a factor they never calculated in advance. A straight forecast requires you to name the first and second finishers in order. A combination forecast – often called a reverse forecast – covers both possible finishing orders between your two selections. Simple enough with two horses: two permutations, double the cost. But start adding a third, fourth or fifth selection and the permutations multiply fast. I have seen newcomers at Ascot pick five horses in a combination forecast thinking they had ten bets on the ticket. The actual number was twenty.
This guide lays out the formula, the cost tables and the critical differences between combination forecasts and exacta wheels so you know exactly what you are paying before the bet goes on.
What a Combination Forecast Covers That a Straight Forecast Does Not
Think of a straight forecast as a sniper shot – you pick horse A to finish first and horse B to finish second, in that exact order. If B finishes first and A second, you lose. A combination forecast is the insurance policy: it covers every possible ordering of your selected horses across first and second place. With two horses, that means two permutations (A-B and B-A). The cost doubles, but so does your coverage.
Where it gets interesting is when you select more than two horses. With three selections you are not just covering two orders – you are covering every possible pair from those three horses, in both orders. That gives you 3 x 2 = 6 permutations. Four horses produce 4 x 3 = 12 permutations. Five horses hit 5 x 4 = 20. The formula is n x (n-1), where n is the number of selected horses. This is a permutation, not a combination, because finishing order matters.
I find that the jump from two to three selections is where most punters underestimate the cost. Two horses at a pound each: 2 pounds total. Three horses at a pound each: 6 pounds total. That is a three-fold increase for adding just one more runner to the ticket. The maths is unforgiving, and it only accelerates from there.
The UK Tote takes a 25% deduction from the exacta pool before distributing dividends. That deduction applies regardless of whether you placed a straight forecast, a combination forecast or a wheel bet – all of them draw from the same pool. The distinction between these structures is purely about how many permutations you cover and how much you pay, not about how the dividend is calculated.
Combination Forecast Formula and Cost Table
I carry this formula everywhere on racedays: total permutations = n x (n-1). Multiply by unit stake and you have the ticket cost. At a 1-pound unit, 2 selections produce 2 permutations for 2 pounds, 3 selections produce 6 for 6 pounds, 4 selections produce 12 for 12 pounds, 5 selections cost 20, 6 selections cost 30, 7 selections cost 42, and 8 selections produce 56 permutations for 56 pounds. At a 2-pound unit, double every figure. I stop at eight because beyond that the cost becomes impractical for almost any bankroll.
The pattern is clear: every additional selection increases the cost by roughly 50% to 70% depending on where you are on the curve. From 4 to 5 selections you add 8 permutations. From 7 to 8 you add 14. The growth is not exponential in the strict mathematical sense, but it feels exponential to your wallet.
Where does the practical ceiling sit? For me, five selections is the outer limit for regular betting. Twenty permutations at a pound is a reasonable spend for a competitive race where I genuinely cannot separate the leading contenders. Beyond five, I switch to a different structure – usually an exacta wheel with a key horse, which controls cost more effectively when I have a strong view on the winner but uncertainty about the runner-up.
The Tote deduction on the exacta pool runs between 16% and 28% depending on pool type, with the standard exacta sitting at 25%. That deduction is baked into the declared dividend, so the figure you see published is already net of the Tote’s commission. Your combination forecast pays the same per-unit dividend as a straight forecast – the extra permutations cost you more upfront but do not change the payout mechanics.
Combination Forecast vs Exacta Wheel: Overlap and Differences
I spent the first two years of my career treating combination forecasts and exacta wheels as interchangeable. They are not. The overlap is real – both involve multiple permutations across first and second place – but the structural logic differs in ways that affect cost and strategy.
A combination forecast selects a group of horses and covers every permutation of every pair within that group. No horse is fixed in any position. Every selection can finish first or second alongside every other selection. The formula is n x (n-1) across all selected runners.
An exacta wheel, by contrast, fixes a key horse in one position – usually first – and fills the other position with some or all remaining runners. The formula for a full exacta wheel with one key horse in first is (n-1), where n is the total number of runners in the race. A part wheel narrows the non-key leg to a chosen subset.
Here is the practical difference. Suppose you fancy three horses in an 8-runner race but cannot separate them. A combination forecast on those three costs 6 permutations. An exacta wheel keying one of those three in first and wheeling the other two through second costs just 2 permutations. The wheel is cheaper, but it only pays if your key horse wins. The combination forecast pays if any pair from your three finishes first and second in either order.
The choice comes down to conviction. If you have a clear view on the winner, an exacta wheel with a key horse is leaner and cheaper. If you rate two or three horses equally and cannot pick the winner among them, the combination forecast gives you broader coverage at a higher price. I use combination forecasts in open races – competitive handicaps, maiden fields with unexposed runners, any card where form is hard to separate. I switch to exacta wheels when one horse stands out and the question is only about what runs on behind it.
One more distinction worth noting: combination forecasts are typically offered by both the Tote and fixed-odds bookmakers, though the mechanics differ. On the Tote you are entering the pool and receiving a share of the dividend. With a bookmaker you are usually getting a computer straight forecast payout, which is calculated by an algorithm rather than a live pool. The returns can differ significantly, and I have seen CSF payouts undercut Tote dividends on well-fancied results while exceeding them when outsiders fill the places. For the full cost mechanics across all wheel bet types in UK racing, the pillar guide covers formulas for exacta, trifecta and superfecta structures together.
How do combination forecasts differ from wheel bets?
A combination forecast covers every permutation of every pair within a selected group of horses – no horse is fixed in any position. A wheel bet fixes a key horse in one position and fills the other position with some or all remaining runners. The combination forecast is broader and more expensive per selection count, while the wheel bet is more targeted and cheaper when you have a strong view on the winner.
Is a combination forecast available with UK bookmakers or Tote only?
Both. The UK Tote offers combination forecasts as part of its exacta pool, where your bet enters a live pool and the dividend is shared among winners after a 25% deduction. Most major UK bookmakers also offer combination forecasts, typically paying via a computer straight forecast algorithm rather than a pool. The same bet can produce different returns depending on which platform you use.
Published by the Horse Racing Wheel bet Calculator team.
