What a Round Robin Is
Picture a betting slip that folds on itself like a poker hand. A round robin stitches together multiple parlays, letting you cover every pairing of your selections. It’s essentially a systematic way to bet on all possible two‑horse combos, three‑horse combos, or whatever size you choose, without buying each parlay separately.
Combinatorial Core
Start with n horses. The number of distinct combos of size k is the binomial coefficient C(n,k)=n!/(k!(n‑k)!). For a typical “2‑way” round robin you pick n = 4 and k = 2, giving C(4,2)=6. Those six mini‑parlays sit side by side on a single ticket. If you crank it up to a “3‑way,” you’re looking at C(4,3)=4 combos, each covering three horses. The math is unforgiving—miss a horse and the whole structure stumbles.
Odds Multiplication
Odds aren’t added, they’re multiplied. Say Horse A is 3.0, B is 4.5, C is 2.2. A 2‑way combo A×B yields 3.0×4.5=13.5, meaning a £10 stake returns £135 if both win. For a 3‑way A×B×C you’d get 3.0×4.5×2.2≈29.7. Multiply the decimal odds for each leg, then subtract one to find net profit per unit stake. The exponential growth is why a round robin can explode quickly—or evaporate just as fast.
Profit Calculation
Take a 4‑horse, 2‑way round robin at £5 per combo. Six combos, total stake £30. If two combos hit, you’ll collect two payouts. Suppose those payouts are £100 and £80. Net profit = (£100+£80)‑£30 = £150. Simple subtraction, but the hidden variable is the probability of multiple hits. Roughly estimate each horse’s win probability as 1/odds. For A (3.0) it’s 33.3%, B (4.5) 22.2%, C (2.2) 45.5%, D (5.0) 20%. The joint probability for any 2‑way is the product of the two chances, then multiplied by the number of combos that contain that pair.
Edge Cases and Pitfalls
Overlapping bets mean you’re betting the same horse multiple times. If that horse crashes, you lose more than a single parlay would. Also, bookmakers trim the payout on round robins; the odds are often reduced by a fraction of a percent. That tiny discount can swing a marginal profit into a loss when you’re playing dozens of combos. The sweet spot lies in choosing horses with high implied probability but generous odds—rare, but not impossible.
Practical Example Using the Site
Jump onto horseracingroundrobin.com and input four selections. The calculator spits out 6 combos, each with its own implied payout. Adjust the stake until the total exposure matches your bankroll. A common trick: set a modest stake on the high‑risk combos, a bigger stake on the low‑risk ones. That way you hedge without blowing the whole ticket.
Actionable Advice
Pick three to four horses with odds between 2.0 and 5.0, run a 2‑way round robin, keep the total stake under 5% of your bankroll, and watch the odds on each combo. If any combo’s implied payout exceeds the total stake by at least 20%, lock it in. Stop.