About this tool
The Round Robin Bet Calculator turns a list of selections into every smaller parlay it contains and totals the cost and payouts. Choosing parlay size k from N selections makes C(N,k) = N! / (k!(N−k)!) combinations; picking several sizes (for example "by 2s and 3s") sums the counts. With four legs, a 2s-and-3s round robin is C(4,2) + C(4,3) = 6 + 4 = 10 parlays, so at a $10 per-parlay stake the total outlay is $100.
Everything runs locally in your browser and nothing you enter is uploaded. Enter a per-parlay stake, one leg's odds per line (American, decimal, or fractional), and the parlay sizes to combine. The tool enumerates every combination, multiplies the decimal odds within each, and reports the number of bets, the total cost, the best case (all legs of every parlay win, so all payouts sum), and the smallest and largest single-combo payout so you can see the spread.
This is a pure math reference and does not place bets or handle real money. Round robins spread risk across overlapping parlays: unlike a single big parlay you can still collect if one leg loses, but you pay for many bets and the best case requires every leg to win. Use it to weigh cost against the payout range before deciding how many selections and sizes to combine.