Parlay Calculator

Parlays (also called accumulators, multis, or combo bets) are among the most popular and most profitable bets for sportsbooks. This calculator reveals the mathematics behind why parlays have such massive house edges and why the "big payout" appeal masks a terrible expected value.

Why Sportsbooks Love Parlays

Every leg you add to a parlay exponentially decreases your win probability while the payout doesn't keep pace with true odds. The result? House edges that can exceed 30% on common parlays, compared to 4-5% on straight bets.

Build Your Parlay

Add legs with American, Decimal, or Fractional odds and see the true mathematics

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Parlay Legs

Standard -110 lines have ~4.5% vig

Why Parlays Are Called "Sucker Bets"

The American Gaming Association reports that parlays generate disproportionately high revenue for sportsbooks relative to the amount wagered. The reason is simple mathematics that this calculator reveals.

When you make a straight bet at standard -110 odds, the sportsbook charges approximately 4.5% vig (vigorish). This is already a significant house edge. But with parlays, something insidious happens: the vig compounds with every leg you add.

The Compounding Effect

Consider two scenarios betting on coin flips (50% probability each):

  • Two separate $100 bets: You face 4.5% house edge on each, for an effective combined edge around 4.5%
  • One $100 parlay on both: The vig compounds, giving the house an edge of approximately 9-10%

As explained in probability theory from Encyclopedia Britannica, when you multiply probabilities together, any small deviation from fair odds gets amplified exponentially.

Did You Know? Professional sports bettors almost never make parlays. The mathematical disadvantage is simply too large. According to betting industry analysis, parlays can account for over 30% of sportsbook profits despite representing a much smaller percentage of total handle.

The Psychology of Parlay Appeal

Despite the terrible mathematics, parlays remain wildly popular. Research into gambling psychology, such as studies documented by the National Institutes of Health, shows why:

  • Availability Heuristic: Big parlay wins get publicized; the countless losses don't
  • Risk-Seeking for Gains: People prefer small chances at big wins over certain moderate gains
  • Entertainment Value: Parlays create excitement watching multiple events
  • Small Stakes: Betting $10 to win $1,000 feels "worth a shot"

Our article on Near Miss Psychology explores how these cognitive biases affect gambling behavior more broadly.

Fixed Odds vs. True Parlays

Many sportsbooks offer "fixed odds" parlay payouts that are actually worse than calculated parlays:

Parlay Size True -110 Payout Typical Fixed Payout Extra Edge to Book
2 legs +264 +260 +0.5%
3 legs +597 +600 Fair
4 legs +1,228 +1,000 +2.5%
5 legs +2,435 +2,000 +3.8%
6 legs +4,793 +4,000 +4.6%

These fixed payouts add additional house edge on top of the already-compounded vig from each leg.

When Parlays Make Mathematical Sense

There are limited scenarios where parlays aren't mathematically terrible:

Correlated Parlays (Often Restricted)

If outcomes are positively correlated (one outcome makes another more likely), parlays can have value. For example: betting a team to win AND the over. However, sportsbooks actively restrict or void correlated parlays.

Taking True Edge Bets

If you genuinely have an edge (positive expected value) on each leg - which is extremely rare - parlaying can amplify your edge. This is why the MIT Blackjack Team sometimes used team play strategies that effectively created positive EV "parlays."

Entertainment Budget

If you treat parlays purely as entertainment with money you're prepared to lose, the mathematical disadvantage is the "price of entertainment" - similar to our analysis in the Gambling Cost Calculator.

Parlay vs. Straight Bet Comparison

The National Council on Problem Gambling emphasizes understanding true odds as part of responsible gambling education. Here's a direct comparison:

Over 1,000 bets at $100 each:
  • Straight bets (4.5% edge): Expected loss of $4,500
  • 2-leg parlays (9% edge): Expected loss of $9,000
  • 4-leg parlays (20% edge): Expected loss of $20,000
  • 6-leg parlays (30% edge): Expected loss of $30,000

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Remember: This calculator is for educational purposes only, designed to illustrate the mathematics of parlay betting. Understanding these odds helps explain why sportsbooks are profitable businesses. If you or someone you know has concerns about gambling, the National Problem Gambling Helpline is available 24/7 at 1-800-522-4700.