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Middles Calculator

Find middle bet opportunities where you bet both sides of a spread or total at different sportsbooks and potentially win both bets. Calculate the probability, expected value, and optimal stake split.

Sport:
Presets

Inputs

ABook A
Decimal: 1.909
VS
BBook B
Decimal: 1.909
$

Results

Expected Value+$5.91+EV Middle
Middle Window
3
3.5
Score margin3 pushes one side and wins the other
Window boundary on key number 3. A push on this number refunds one side while the other wins; that outcome is priced in the table below.
Chance the number lands in the window15.00%
NFL margin table (share of games decided by exactly that number, applied to the favourite's side)
Optimal Stake Split
Book A$100.00
50.0%
Book B$100.00
50.0%
Outcome Scenarios
ScenarioProfit / Loss
Margin exactly 3: Favorite pushes, Underdog wins 15.0%+$90.91
Side A wins only 85.0% for either miss -$9.09
Side B wins only -$9.09
Middle Window0.5 pts
Guaranteed Loss$9.09
ROI+2.95%
Breakeven Prob9.09%
Middling vs Straight Bet
Middle EV (both sides)+$5.91
Straight bet A only ($200.00)$9.09
Straight bet B only ($200.00)$9.09
Middling has higher EV than either straight bet alone.

Understanding Middle Bets

What is a Middle Bet?

A middle bet occurs when you find different spreads or totals at two sportsbooks, creating a "window" where the final result could land. If it does, both bets win. For example, if you bet Team A -3 at Book 1 and Team B +4.5 at Book 2, any final margin of 4 means both bets win. The key is finding line discrepancies between books.

Middles vs Arbitrage

In arbitrage, you guarantee a profit regardless of outcome. In a middle, you accept a small guaranteed loss if the middle doesn't hit, but win big if it does. Middles are higher variance but can have better long-term expected value because sportsbooks are less likely to limit players betting different sides at different spreads compared to obvious arb patterns.

Key Numbers and Middles

In NFL betting, certain margins occur far more frequently than others. The number 3 accounts for roughly 15% of final margins, and 7 accounts for about 10%. Middles that cross these key numbers are significantly more valuable. A middle spanning -3 to +4 in the NFL includes the key number 3, making it one of the most profitable middle opportunities available.

Risk Management for Middles

Optimal middle betting requires careful bankroll management. Since most middles will miss, you must size bets so the guaranteed loss is small relative to your bankroll (typically 1-2%). The key is ensuring the expected value is positive over hundreds of middles. Use the optimal stake split calculator to minimize your worst-case loss while preserving upside when the middle hits.

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