A round robin takes 3 or more selections and automatically generates every smaller-parlay combination of a chosen size. Instead of one all-or-nothing 4-leg parlay, you can have six separate 2-leg parlays from the same selections. Lower max payout, but partial wins still cash.
How the combinations work
You pick your selections (also called "teams" at most sportsbooks) and pick a parlay size to combine them into. The book then creates every possible parlay of that size. The math is straightforward combinatorics:
- 3 selections, 2-leg parlays: 3 doubles
- 4 selections, 2-leg parlays: 6 doubles
- 4 selections, 3-leg parlays: 4 trebles
- 5 selections, 2-leg parlays: 10 doubles
- 5 selections, 3-leg parlays: 10 trebles
- 6 selections, 3-leg parlays: 20 trebles
- 8 selections, 4-leg parlays: 70 four-leg parlays
You can also stack: a "by 2s and 3s" round robin on 4 selections gives you the 6 doubles AND the 4 trebles — 10 bets total.
Worked example: 4 NFL games, rounded by 2s
You like the spreads on 4 Sunday games, each at −110. Stake $10 per bet.
- Selections: A, B, C, D
- Combinations: AB, AC, AD, BC, BD, CD — six 2-leg parlays
- Total stake: 6 × $10 = $60
- Each 2-leg parlay at −110/−110 pays: 1.9091 × 1.9091 × $10 = $36.45 ($26.45 profit)
- If all 4 selections win: all 6 doubles cash → 6 × $36.45 = $218.70 total payout, $158.70 profit
- If 3 of 4 win (say A, B, C win, D loses): the three doubles not containing D cash → AB, AC, BC win → 3 × $36.45 = $109.35 payout, $49.35 profit
- If 2 of 4 win (say A, B win, C and D lose): only AB cashes → $36.45 payout, $23.55 loss on the $60 total stake
- If 1 or 0 of 4 win: all 6 doubles lose → $60 total loss
Compare to a single 4-leg parlay at −110 with $60 stake: $797.00 payout if all 4 win, $0 if you miss even one. The round robin trades the big payout for the chance to recover something when 3 of 4 hit.
When a round robin makes sense
Round robins are most useful when:
You have moderate confidence on several selections but not full confidence on any one. You like a slate of 4-5 games but don't want all-or-nothing risk. Splitting into doubles gives you reasonable upside if 3+ hit.
You want exposure to multiple parlay sizes from the same picks. The "by 2s and 3s" option lets you cover both the conservative doubles and the higher-upside trebles in one ticket.
You want the math to feel less brutal when one leg misses. Losing a single leg of a straight parlay zeroes it out. With a round robin, losing one leg still leaves multiple combinations alive.
When a round robin doesn't make sense
The math doesn't beat the math. A round robin has the same per-leg vig as a straight parlay — there's no edge created by combinatorics. If your selections aren't profitable individually, splitting them into combinations doesn't fix that.
Round robins also rack up large total stakes fast. A 6-selection round robin by 3s is 20 trebles — at $10/bet, that's $200 committed. If you're stake-constrained, a single smaller parlay or a few standalone bets might serve you better.