Calculating parlay payouts yourself takes 30 seconds and lets you verify that a sportsbook is paying you what the parlay is worth (or see how much they're taking in additional margin).
The Parlay Calculation Method
Parlay payouts are calculated by multiplying the decimal odds of each leg together, then converting back to American odds.
Step 1: Convert each leg to decimal odds
- American -110 → decimal: 1 + (100/110) = 1.909
- American +150 → decimal: 1 + (150/100) = 2.500
- American -120 → decimal: 1 + (100/120) = 1.833
Step 2: Multiply all decimal odds together
- 3-team parlay: 1.909 × 2.500 × 1.833 = 8.74 decimal
Step 3: Convert back to American odds
- 8.74 > 2.00, so: (8.74 - 1) × 100 = +774
Your 3-team parlay would theoretically pay +774 at fair odds.
Step 4: Compare to actual book payout
- If the book offers +720, they're taking an additional ~7% margin on the parlay structure
Reference Table for Common Parlays
| Legs | All -110 Legs | Theoretical Payout | Typical Book Payout | |———|———————|—————————-|——————————-| | 2 | 2 legs at -110 | +264 | +260 | | 3 | 3 legs at -110 | +596 | +595 | | 4 | 4 legs at -110 | +1228 | +1200 | | 5 | 5 legs at -110 | +2435 | +2300 |
Books are generally fair on 2-3 leg parlays but take additional margin on 4+ leg parlays.
Why This Matters
SGPs (same-game parlays) are where the biggest gap appears. A 4-leg SGP where independent math would suggest +1200 might be offered at +450 due to correlation adjustment and additional book margin. Knowing the fair value helps you identify when a promotion (like a 25% boost) actually closes the gap.
[Track your parlay ROI vs. single-bet ROI in Oddible →]
