Free Sports Betting Middle Calculator

Choose Total if you're middling an Over/Under, or Spread if you're middling two teams' point spreads. Enter the point and odds for Leg A and Leg B exactly as each sportsbook shows them — in spread mode, Leg A and Leg B are the two opposing teams, each at a different book.

Then enter your total bankroll. The calculator splits it between both legs and shows the window size, your profit if the middle hits, your worst case if it misses, and an estimated probability that the result lands inside the window.

A middle bet covers both sides of the same game at different sportsbooks, using lines that are far enough apart to create a range of outcomes where both bets win at once. It happens when two books disagree enough on where to set a spread or total.

For example: Book A has the Chiefs at -1.5, Book B has the Eagles at +3.5. Bet Chiefs -1.5 at Book A and Eagles +3.5 at Book B. If the Chiefs win by exactly 2 or 3, both bets win. Any other result, you win one and lose the other.

For totals, the window is simply the gap between the two points:

Window = Under point − Over point

For spreads, Leg A and Leg B are opposite teams at different books, so the window is their points added together:

Window = Leg A point + Leg B point

The estimated hit probability uses the identity P(both) = P(Leg A) + P(Leg B) − 100%, where each leg's probability is 1 ÷ its decimal odds. This holds exactly given the two thresholds, but because sportsbook odds bake in the vig, it's a conservative estimate rather than a precise model of the game itself.

The calculator uses equal-value sizing so both legs return the same amount if either wins alone:

Stake A = Bankroll × Decimal B ÷ (Decimal A + Decimal B)

Profit if the middle hits is the combined return from both legs winning, minus your total stake. Your worst case if it misses is the same regardless of which single leg wins — that symmetry is exactly what equal-value sizing is for.

Use it when you've spotted a potential middle on your own, or want to double-check one from our Middle Finder. Enter the exact lines shown at each book to confirm the window is real and get the precise dollar amounts to bet on each leg.

Always verify the odds at the sportsbook before placing your bets — lines move fast, and a stale price can shrink or erase the window entirely.