Acca Builder
Build football accumulators with live expected value, Kelly-optimised staking, and leg-by-leg colour-coded value detection.
Negative EV. The bookmaker has the edge here. Consider different selections or wait for better odds.
Leg-by-Leg EV Breakdown
| Selection | Odds | Model Prob | Fair Odds | Leg EV |
|---|---|---|---|---|
| Man City Win | 1.40 | 70.0% | 1.43 | -2.0% |
| Arsenal Win | 1.53 | 65.0% | 1.54 | -0.5% |
How Acca Math Works
An accumulator (parlay) multiplies the decimal odds of each leg together. If you combine three selections at 1.50, 2.00, and 1.80, the total odds are 1.50 x 2.00 x 1.80 = 5.40. A $50 stake would return $270 if all three win.
The implied probability of the parlay is 1 / 5.40 = 18.5%. That means the bookmaker thinks you have an 18.5% chance of winning. Your model probability is your own estimate — if you believe each leg has a higher chance than the odds suggest, the parlay has positive expected value.
Vig compounds in parlays. If each leg has 5% vig, the total vig on a 5-leg parlay is roughly 1 - (0.95)^5 = 22.6%. This is why bookmakers love accumulators — the edge compounds exponentially.
Kelly staking for parlays uses the formula: f* = (p x O - 1) / (O - 1), where p is your model's parlay probability and O is the bookmaker's total parlay odds. Because parlays have higher variance, most professionals use fractional Kelly (1/4 or 1/2 of the full Kelly amount).
Acca Formula: Total Odds = O1 × O2 × ... × On Fair Prob = P1 × P2 × ... × Pn EV = Fair_Prob × Total_Odds × Stake - Stake Kelly f* = (Fair_Prob × Total_Odds - 1) / (Total_Odds - 1) Example (3-leg): Leg 1: 1.50 × 70% Leg 2: 2.00 × 52% Leg 3: 1.80 × 58% Total odds = 5.40 Fair prob = 21.1% EV = 0.211 × 5.40 × 50 - 50 = +7.0 (+14.0%) Full Kelly = (0.211×5.40-1)/(5.40-1) = 6.5% of bankroll