How to Calculate Parlay Odds: The Math Behind Multi-Leg Bets
Parlay odds are calculated by multiplying the decimal odds of each leg together. Understanding this math helps you evaluate whether a parlay is worth taking.
By
Eric Pauly
Feb 8, 2026
8 min read
Why You Should Know How to Calculate Parlay Odds
A parlay combines multiple bets into a single wager where every leg has to win for the bet to pay out. The appeal is simple: bigger payouts than placing each bet individually. But the math behind how those payouts are calculated is something most bettors never learn. They rely on the sportsbook to show them the combined odds without understanding whether those odds are fair, how much juice the book is taking on the parlay, or how each additional leg changes the risk profile.
I started building my own parlay calculator spreadsheet during the 2024 NFL season after noticing that the same 3-leg parlay paid differently at different sportsbooks. The payout differences were not small. On a $100 bet, I found variations of $30 to $50 depending on which book I used. That realization made it clear that understanding the underlying math is not optional if you are going to bet parlays regularly. This guide walks through the step-by-step calculation, from converting American odds to decimal odds, to multiplying the legs together, to understanding how the juice compounds. For a broader look at what parlays are and when they make sense, the parlay explained guide covers the basics.
article Summary
To calculate parlay odds, convert each leg from American odds to decimal odds, multiply all the decimal odds together, then convert back to American odds. A 3-leg parlay at -110 per leg pays roughly +596 (about 6 to 1). Each additional leg multiplies both the potential payout and the probability of losing. Sportsbooks also add extra juice to parlays, so comparing parlay prices across books matters.
Step 1: Convert American Odds to Decimal Odds
The Conversion Formulas
Parlay math works in decimal odds because you need to multiply the odds of each leg together, and that only works cleanly in decimal format. To convert American odds to decimal odds, use these formulas. For negative American odds (like -110): Decimal Odds = 1 + (100 / |American Odds|). So -110 becomes 1 + (100/110) = 1.909. For positive American odds (like +150): Decimal Odds = 1 + (American Odds / 100). So +150 becomes 1 + (150/100) = 2.500. These conversions are the foundation of every parlay calculation. If you want a deeper walkthrough of converting between odds formats, the calculating odds guide covers all the formulas.
Why Decimal Odds Make Parlays Easy
Decimal odds represent your total return per dollar wagered, including your original stake. If the decimal odds are 1.909, a $1 bet returns $1.909 total ($1 stake + $0.909 profit). This format makes it straightforward to chain multiple bets together because you simply multiply each leg's decimal odds. The product gives you the combined decimal odds for the parlay. Trying to do this math directly with American odds would require separate calculations for each leg and a complex formula to combine them. Decimal odds turn it into basic multiplication.
Step 2: Multiply the Decimal Odds Together
The Core Calculation
Once every leg is in decimal format, multiply them all together. Using the example from Step 1: 1.909 x 2.500 x 1.769 = 8.443. This number is your combined decimal odds. It means a $1 bet returns $8.443 total if all three legs win. For a $100 bet, your total return would be $844.30, which includes your $100 stake plus $744.30 in profit. The math is the same regardless of how many legs you add. Four legs means four numbers multiplied together. Five legs means five. Each additional leg makes the product larger (bigger potential payout) but also less likely to hit.
Converting Back to American Odds
If you want to express your parlay in American odds, convert the combined decimal odds back. For decimal odds above 2.0: American Odds = (Decimal Odds - 1) x 100. So 8.443 becomes (8.443 - 1) x 100 = +744. For decimal odds below 2.0 (rare for parlays since parlays almost always pay above even money): American Odds = -100 / (Decimal Odds - 1). In practice, most parlays with 2 or more legs will have combined decimal odds well above 2.0, so you will usually use the first formula.
What the Implied Probability Tells You
You can also convert the combined decimal odds to an implied probability: Implied Probability = 1 / Decimal Odds. For our 8.443 example: 1 / 8.443 = 11.84%. That means the parlay has roughly a 12% chance of hitting according to the odds. The actual probability of winning may be higher or lower depending on whether you have an edge on each leg. Understanding the implied probability helps you compare the parlay to a prop bet or a straight bet at similar odds and decide which offers the better value.
Step 3: Understand How Juice Compounds in Parlays
The Juice Multiplier Effect
Every leg of a parlay carries its own juice, and when you multiply the odds together, the juice compounds. A single -110 bet has about 4.76% juice. A 2-leg parlay at -110 per leg does not have 9.52% juice. The math is multiplicative, not additive. The actual combined juice on a 2-leg -110/-110 parlay works out to roughly 9.3%, and a 3-leg parlay is around 13.6%. By the time you get to a 5-leg parlay, the compounded juice can exceed 20%. This is one of the primary reasons sportsbooks promote parlays aggressively. The vig scales up with every leg you add.
Sportsbook Parlay Tax
Beyond the compounding juice on each leg, some sportsbooks apply an additional markdown on parlay payouts. This is sometimes called "correlated parlay restrictions" or simply reduced parlay odds. A true odds parlay at -110/-110 for two legs should pay +264. Some sportsbooks pay +260 or even lower on the same combination. The difference is an extra cut the book takes on top of the per-leg juice. Checking the actual payout against your calculated fair payout tells you how much extra the sportsbook is charging. This is another reason line shopping for parlays matters. After comparing parlay payouts across five sportsbooks on the same 3-leg NBA parlay last season, I found a $42 difference between the best and worst payout on a $100 bet.
Why This Math Matters for Your Strategy
Understanding juice compounding changes how you think about parlay construction. A 2-leg parlay with genuine edges on both legs can still be a +EV bet because the compounded juice is manageable. A 6-leg parlay, even with slight edges on every leg, often becomes -EV because the juice compounds past the point where your edges can overcome it. There is a practical ceiling on how many legs a parlay can have before the math turns against you, and knowing how to calculate the juice helps you find that ceiling for your specific bets. The parlay strategy guide goes deeper into how to construct parlays that account for this reality.
Tools for Parlay Odds Calculation
When to Use a Parlay Calculator
While the manual calculation is straightforward once you understand it, doing the math by hand on a 4 or 5-leg parlay gets tedious. Parlay calculators built into odds comparison tools speed up the process and reduce errors. They also let you quickly compare what the same parlay pays at different sportsbooks. OddsJam has a parlay builder that pulls real-time odds and calculates your expected payout across multiple books in seconds. This makes it easy to identify which book gives you the best parlay price before you place the bet.
Comparing Parlay Payouts Across Books
Different sportsbooks calculate parlay payouts using different methods. Some use true mathematical odds (multiplying decimal odds of each leg), while others use preset parlay payout tables that may pay less than the true calculated amount. The only way to know if you are getting fair value is to calculate the true odds yourself and compare. If your calculation says a parlay should pay +600 and the sportsbook is offering +575, you know the book is taking an extra 4% off the top. Having accounts at multiple sportsbooks and checking the parlay price at each one is the same line shopping principle that applies to straight bets, just with higher stakes per bet.
Building a Simple Spreadsheet
If you prefer to calculate parlays yourself, a basic spreadsheet does the job. Column A holds the American odds for each leg. Column B converts those to decimal odds using the formulas from Step 1. A single cell multiplies all the decimal odds together to give you the combined odds. From there, you can add cells for the implied probability, the payout on any stake amount, and the juice percentage. Building this once takes about 15 minutes and gives you a tool you can use for every parlay going forward. I built mine during the 2024 NFL season and have used it on every multi-leg bet since then to sanity-check what the sportsbook is offering.
Final Thoughts
Calculating parlay odds is a three-step process: convert to decimal, multiply the legs together, and convert back if you want American odds. The math itself is not complicated, but the insights it provides are valuable. Once you can calculate a parlay payout independently, you can compare your number to what the sportsbook is offering and see exactly how much juice they are adding. You can also evaluate whether the implied probability of hitting the parlay is realistic given your confidence in each leg.
The biggest takeaway from understanding parlay math is that juice compounds with every leg you add. A 2-leg parlay has manageable juice. A 5-leg parlay has significant juice working against you. That does not mean long parlays are always bad, but it does mean you should go in with your eyes open about the mathematical cost. For more on building parlays that account for these dynamics, the parlay betting strategy guide covers construction approaches that balance payout potential with realistic hit rates.
Parlay Odds Calculation FAQ
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