Definition
A round robin is an automatic set of smaller parlays built from a larger pool of picks. Instead of placing one parlay that needs every leg to win, the sportsbook creates every possible parlay of a chosen size from your selections.
The count formula is:
number of parlays = n! / (r! × (n - r)!)
where n is the number of picks and r is the size of each smaller parlay.
Worked Example
You choose four teams, all at -110, and make a “2-pick round robin.” That creates every 2-team parlay from the four picks:
4! / (2! × 2!) = 6 parlays
If you stake $10 per parlay, the total risk is $60.
A $10 two-leg parlay at -110 and -110 pays about $26.45 total, including the $10 stake, if both legs win. If three of your four picks win, then three of the six two-leg parlays cash, returning about:
3 × $26.45 = $79.35
Your profit is:
$79.35 - $60 = $19.35
Why It Matters
A round robin helps when you like several picks but do not want one losing leg to erase the whole bet. It can reduce all-or-nothing parlay risk, but the total stake rises quickly as more combinations are added.