A round robin can cash after a bad pick without coming close to its maximum payout.
Take four selections entered as two-leg parlays. That creates six separate doubles. If one selection loses, the three doubles containing it also lose; only the three combinations made from the remaining winners return money. The wager survived, but half its tickets did not.
Each parlay is settled independently, using its own stake and the combined prices of its legs. A surviving pair of short-priced favorites may pay far less than a pair containing underdogs. Stake setup matters too: “$5 per combination” means $30 risked across six doubles, while “$30 total” divides that amount among them. A reliable calculator therefore needs the selection odds, parlay size, surviving picks, and whether the entered stake applies per combination or to the entire round robin.
A round robin creates every possible parlay of a chosen size from a larger group of selections. For example, four picks entered as two-leg parlays produce six combinations: AB, AC, AD, BC, BD, and CD.
The calculator treats each combination as its own bet. It converts the odds for the selections in AB into one potential return, repeats the process for AC and the remaining pairs, then adds the returns from combinations that win. This differs from trying to estimate a standard parlay payout, where every selection belongs to one all-or-nothing ticket.
That distinction matters because the sub-parlays can have different prices. A pair containing two short favorites may return much less than a pair containing two underdogs, even when both receive the same stake.
For a four-pick, two-leg round robin:
A single losing pick therefore eliminates only the combinations containing that selection. The other sub-bets remain live and are settled at their own odds.
Record the total number of legs. This determines how many distinct combinations the round robin contains.
Write down the odds beside each selection, keeping the displayed precision rather than rounding early.
Note whether the bet uses two-leg, three-leg, or larger combinations.
Convert fractional or American prices to decimal odds before doing any multiplication. Mixing formats produces meaningless results.
Check whether the stated amount is the total outlay or the stake on each combination. Some calculators split stakes across the combinations, while others apply the entered amount to every one.
Five selections arranged as three-leg combinations create 10 separate bets. A £10 total stake assigns £1 to each combination. A £10 per-combination stake creates a £100 total outlay.
That distinction changes every return figure, so it should be settled before any winning combinations are priced.
A round robin’s bet count is calculated with the combinations formula:
C(n,r) = n! / [r!(n-r)!]
Here, n is the total number of selections, while r is the number used in each sub-parlay. The exclamation mark denotes a factorial: for example, 4! = 4 × 3 × 2 × 1.
| Round robin | Calculation | Sub-parlays | Outlay at $5 each |
|---|---|---|---|
| 3 by 2s | C(3,2) | 3 | $15 |
| 4 by 2s | C(4,2) | 6 | $30 |
| 4 by 3s | C(4,3) | 4 | $20 |
| 5 by 2s | C(5,2) | 10 | $50 |
“4 by 2s,” for instance, creates every distinct two-selection pairing from four picks. The total outlay equals the number of sub-parlays multiplied by the stake per sub-parlay. Adding only one or two selections can therefore increase the cost much faster than expected.
At $5 per sub-parlay, moving from 3 by 2s to 5 by 2s raises the outlay from $15 to $50.
For positive odds, use 1 + (odds ÷ 100); +150 becomes 2.50. For negative odds, use 1 + (100 ÷ absolute odds); −200 becomes 1.50.
A two-leg combination at 2.50 and 1.50 has combined decimal odds of 3.75. Each sub-parlay is calculated separately because it contains a different set of prices.
Multiply the combined decimal odds by the per-combination stake. At $5, odds of 3.75 produce a $18.75 gross return.
Gross return includes the original $5 stake. Profit is $18.75 minus $5, or $13.75.
Add the gross returns from every winning combination, then subtract the full original outlay. If six combinations were staked at $5 each, the outlay was $30—including stakes on combinations that lost.
Equal stakes do not mean equal returns. A combination containing longer-priced legs has higher combined odds and therefore pays more when it wins.
A displayed stake may mean per combination or total across the round robin. A $30 total stake spread over six combinations means $5 per combination; $30 per combination means a $180 outlay.
Consider three selections with decimal odds of A: 1.50, B: 2.00, and C: 3.00. Playing them as a round robin by 2s creates three doubles: A+B, A+C, and B+C.
Assume $10 is staked on each double. The full outlay is therefore $30.
| Double | Combined odds | Stake | Potential gross return | Sub-parlay profit |
|---|---|---|---|---|
| A+B | 1.50 × 2.00 = 3.00 | $10 | $30 | $20 |
| A+C | 1.50 × 3.00 = 4.50 | $10 | $45 | $35 |
| B+C | 2.00 × 3.00 = 6.00 | $10 | $60 | $50 |
The profit in the table applies to each double on its own. The overall round-robin result must account for the entire $30 outlay, including losing combinations.
This is why “two winners” does not identify a single payout. The identity of those winners matters: the higher-priced B+C pair returns twice as much as A+B, despite both outcomes containing exactly two successful selections.
A four-pick round robin by 2s creates six separate pairs: AB, AC, AD, BC, BD, and CD. If w selections win, the number of successful pairs is calculated as C(w, 2).
| Winning selections | Successful pairs | Calculation |
|---|---|---|
| 2 | 1 | C(2,2) |
| 3 | 3 | C(3,2) |
| 4 | 6 | C(4,2) |
With only two winners—A and B, for example—AB is the sole paying combination. If A, B, and C win, AB, AC, and BC all succeed. A clean sweep makes every pair successful. Zero or one winner produces no successful pair.
The pair count does not reveal the amount returned. Three successful pairs containing short-priced favorites may pay less than one successful pair built from two underdogs. Each pair also has its own stake, combined odds, and settlement status.
For reliable records, list all six combinations and settle them one at a time rather than multiplying a generic payout by the number of winners. A practical approach is to log the combinations in Google Sheets, with columns for both selections, pair odds, stake, result, and gross return. This also makes voids, pushes, or adjusted prices easier to handle without distorting the other pairs.
A clean calculator normally assumes posted odds and equal stake allocation across every sub-parlay, unless the bet slip states otherwise. Sportsbook settlement rules can change either the qualifying combinations or their returns.
A push or void does not always kill a combination. Commonly, that leg is removed and a three-leg parlay becomes a two-leg parlay, but rules for a voided parlay leg vary by operator. Ties may settle as pushes, wins, losses, or partial results depending on the market, while abandoned events may be voided only if specified completion conditions are not met.
Dead heats are different from ordinary ties: the stake or winnings for the affected selection may be divided by the number of tied finishers. This can reduce every sub-parlay containing that selection.
Odds boosts can increase eligible returns, while maximum-payout caps can limit them. Sportsbooks may also round each sub-parlay separately rather than rounding only the final total, producing small discrepancies.
Finally, some correlated selections cannot be combined at all, or may receive adjusted prices. A calculator using the displayed standalone odds cannot reproduce those restrictions unless the accepted slip provides the revised terms.
The accepted bet slip and sportsbook rulebook take priority over a theoretical calculation. Check the settlement inputs before treating a difference as an error.
Identify wins, losses, pushes, voids, dead heats, and any event-completion rule.
Verify boosts, revised combination odds, payout caps, and restrictions on related selections.
Compare stake allocation and per-combination rounding with the values printed on the slip.
A reliable check starts before the wager: confirm the selection count, combination size, stake per sub-bet, and total outlay. After settlement, inspect every sub-parlay, mark the settled legs, and add gross returns only from combinations that remain winners. Net profit or loss is that sum minus the entire original stake.
Calculator figures are estimates, not settlement decisions. The sportsbook’s rules on voids, rounding, dead heats, promotions, and payout limits always control.
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