The NFL Futures Tax: 30%+ Overround, the Harville Model, and When to Bet Anyway
On a standard -110/-110 game line, both sides of the bet add up to 104.76% implied probability. The 4.76% gap is the book's margin. You know this going in.
On a Super Bowl futures board with all 32 teams listed, that same math produces a number closer to 130%. Not 104.76%. One hundred and thirty percent.
That 25-point gap is the structural tax every futures bettor pays before a single snap. Most bettors don't know it exists. This piece explains where it comes from, why longshots carry an even heavier share of it, and the narrow set of conditions where futures bets remain worth making.
The Baseline: Overround on a Two-Sided Market
Start with the familiar. A -110 game line implies a win probability of:
Implied probability = |odds| / (|odds| + 100)
= 110 / (110 + 100) = 52.38%
Both sides at -110 sum to 104.76%. The book keeps 4.76 cents of every dollar bet, on average, assuming balanced action. That is the vig on a binary market.
A game line is a two-outcome market. One team wins. The math is clean, and the overround is small.
Why Futures Are Structurally Different
A Super Bowl futures market is a 32-outcome market. Every team has a price. Every price implies a probability. Every implied probability adds to the running total.
On a binary market, the book can post symmetrical odds and keep the overround low. On a 32-team market, every outcome you add to the board contributes its own implied probability slice. The math compounds quickly.
The national hold rate of 10.15% in 2025 reflects the mix of all bet types. Parlays pull that number up. So does futures volume. The pure game-line hold sits closer to 4-5%. Futures volume drags the average toward 10% because the overround on each futures board is so much higher.
The Math: Calculating the Current NFL Futures Overround
For positive American odds, the implied probability formula is:
Implied Probability = 100 / (Odds + 100)
Example: Rams +550 → 100 / (550 + 100) = 100 / 650 = 15.38%
Here is that calculation applied to 18 teams on DraftKings' current NFL Super Bowl futures board as of September 2026:
| Team | DK Odds | Implied Probability |
|---|---|---|
| LA Rams | +550 | 15.38% |
| Seattle Seahawks | +950 | 9.52% |
| Baltimore Ravens | +950 | 9.52% |
| Buffalo Bills | +1000 | 9.09% |
| Kansas City Chiefs | +1500 | 6.25% |
| Philadelphia Eagles | +1600 | 5.88% |
| New England Patriots | +1600 | 5.88% |
| LA Chargers | +1600 | 5.88% |
| Green Bay Packers | +1600 | 5.88% |
| San Francisco 49ers | +1700 | 5.56% |
| Houston Texans | +1800 | 5.26% |
| Detroit Lions | +1800 | 5.26% |
| Denver Broncos | +2000 | 4.76% |
| Cincinnati Bengals | +2200 | 4.35% |
| Dallas Cowboys | +2500 | 3.85% |
| Chicago Bears | +2500 | 3.85% |
| Jacksonville Jaguars | +3000 | 3.23% |
| Tampa Bay Buccaneers | +5000 | 1.96% |
| 18 of 32 teams total | 111.36% |
Eighteen teams. Already at 111.36%. The remaining 14 teams, including long shots like the Las Vegas Raiders at +15000, contribute additional implied probability. The full 32-team board sums to approximately 130%.
That 30% overround means: even if you have the winner completely right, you are fighting a 30-point structural headwind from the moment you place the bet.
The Harville Model: How Books Price Multi-Entry Fields
Books don't set futures prices by guessing. They use a systematic probability model. The foundational paper is David Harville's 1973 work in the Journal of the American Statistical Association, "Assigning Probabilities to the Outcomes of Multi-Entry Competitions."
Harville's model starts with each competitor's win probability. From that single input, it derives the probability of any ordering of finishers. The model assumes an underlying distribution of performance where the probability that team i finishes second, given that team j won, is:
P(i finishes 2nd | j won) = P(i wins) / [1 - P(j wins)]
More generally: P(any ordering) = product of conditional win probabilities at each stage
In practice, books start with their estimated win probability for each team, derive a theoretical "fair" futures price, then apply a margin by scaling all probabilities down proportionally. The scaling is what produces the overround.
The Harville model was developed for horse racing parimutuel markets but applies directly to any multi-entry competition with a defined winner. Super Bowl futures are that market.
The Favorite-Longshot Bias: Overround Is Not Distributed Evenly
Here is where the math gets worse for public bettors.
In 1988, Richard Thaler and William T. Ziemba published "Anomalies: Parimutuel Betting Markets: Racetracks and Lotteries" in the Journal of Economic Perspectives. They documented a systematic pattern: bettors consistently overbet longshots relative to their true win probability, and underbet favorites.
The consequence in a futures market: books shade their prices to exploit this bias. The margin is fatter on the longshots, because that is where the public money flows regardless of price. The Rams at +550 carry a relatively thin margin. The Jaguars at +3000 carry a proportionally larger one.
A 2025 study by Hegarty and Whelan in Applied Economics confirmed this in large-scale data. They showed that when favorite-longshot bias exists, the average bettor's loss rate exceeds what the headline overround would imply. The overround understates the true cost because the bias concentrates margin on the outcomes bettors want most: the hopeful longshot picks.
The headline: a 30% overround on the board. The reality: the teams the public backs most at long prices carry 35-40% effective margins, while the top two or three favorites carry closer to 20-25%. The stated overround is an average that understates what most bettors pay.
How to Normalize a Futures Field
The right question to ask before placing any futures bet: what does this odds price imply about true probability, after removing the vig?
The method is straightforward. Compute implied probability for every team. Sum all implied probabilities. Divide each team's implied probability by that sum.
Fair probability (team i) = Implied Probability (team i) / Sum of all Implied Probabilities
Example: Rams at +550 → 15.38% implied
Full board sums to ~130%
Fair probability = 15.38% / 1.30 = 11.83%
Fair odds = (1 / 0.1183) - 1 = +745 equivalent
DK posts +550. Fair price is +745. You are getting less than 74 cents on the dollar.
Run this calculation for every team on the board. You will find that every single team's posted odds are worse than the fair odds derived from normalizing the field. That is the structure of the market. There is no team where the math accidentally works in your favor through overround alone.
The Oxford Economic Papers 2025 study "Market Structure and Prices in Online Betting Markets" confirms this: normalized implied probabilities are unbiased estimates of true probabilities, but the posted odds are not. The posted odds systematically understate your true break-even probability.
Why the Time Horizon Adds Another Layer of Margin
Game lines settle within a few hours. Futures bets lock your capital for months.
A Super Bowl futures bet placed in September ties up your bankroll through February. That is five months of opportunity cost. If your locked capital carries a fair return of, say, 5% annually, a six-month future needs to overcome both the 30% overround and the locked-capital cost before it becomes net-positive.
Books also reserve the right to void or adjust futures when teams are sold, coaching staff changes dramatically, or players retire. Settlement rules vary by book. Read the specific terms before placing any multi-month futures position. Some books settle on the opening-week starter; others require the player to play a minimum number of snaps. Check the futures rules on the specific market you are betting.
The Three Windows Where Futures Bets Still Make Sense
None of the above means futures bets are always wrong. The structure is bad. There are specific conditions where betting futures produces positive expected value despite the overround:
Window 1: Early Opening Lines
Opening futures prices for the NFL season go up weeks before the season starts, sometimes months before. At that point, the market is thin and books have not yet adjusted for training camp news, injuries, or sharp money. If you have a strong signal on a team based on offseason moves before the books have fully repriced, the overround is the same as in-season, but you are getting a team's true price before the market fully reflects the information.
The window closes fast. Once sharps hammer a line, the odds compress. Getting +1800 on a team you believe is a true +1200 is the only legitimate way to beat the structural overround.
Window 2: Major News Events Mid-Season
When a starting quarterback goes down in Week 3, futures odds on that team collapse overnight. Other teams adjust upward. The repricing window, when books are slow to update or when sharp money has not fully processed the news, is where informed bettors find short-term value.
The edge evaporates in hours, not days. By the next morning, every book has repriced. If you see a line before the market adjusts, act immediately.
Window 3: Line Shopping Across Books
Different books set different futures prices for the same team. A team at +1600 at DraftKings might be +1800 at FanDuel or +2000 at BetMGM. That 400-point swing represents a meaningful difference in implied probability: +1600 implies 5.88%, +2000 implies 4.76%.
On a game-line bet, line shopping saves you a half-point or a few cents of vig. On a futures bet at long odds, finding a +2000 versus a +1600 on the same team means your breakeven probability drops from 5.88% to 4.76%, a full percentage point. Over many futures bets, that gap compounds into real money.
The table below shows how much the no-vig break-even probability shifts across common futures odds ranges:
| Posted Odds | Implied Prob | No-Vig Break-Even (at 130% board) | Odds You'd Need at Fair Price |
|---|---|---|---|
| +500 | 16.67% | 12.82% | +680 |
| +1000 | 9.09% | 6.99% | +1330 |
| +1500 | 6.25% | 4.81% | +1980 |
| +2000 | 4.76% | 3.66% | +2631 |
| +3000 | 3.23% | 2.48% | +3930 |
| +5000 | 1.96% | 1.51% | +6523 |
The "Odds You'd Need at Fair Price" column shows what the posted price would need to be for you to break even, after removing the 30% overround. A team at +3000 would need to be posted at +3930 to represent fair value. The posted price gives you 74 cents on the dollar.
That ratio holds across almost every team on the board. You are structurally getting worse than fair value. The three windows above are the exceptions: early pricing, major news, and cross-book line shopping.
What This Means for Your NFL Futures Strategy
Four conclusions from the math:
First, if you want to bet NFL futures, pick one team and go through at least three books before placing the bet. The odds dispersion on futures is wider than on game lines, and the payoffs are large enough that an extra 200-400 points of odds matters.
Second, never bet a futures field where you "like several teams." Every bet is independent. Betting four teams on the same futures market does not diversify your exposure. It multiplies the overround you pay.
Third, the longshot bet you love because "it only costs $20" is where the book makes the most money per dollar. The effective margin on a +8000 shot is not 30%. It is closer to 50% or more, because the favorite-longshot bias concentrates the book's profit on those prices. Thaler and Ziemba documented this in racetrack markets, and the same pattern holds in sports futures.
Fourth, if your futures betting record is break-even or slightly losing, the math above is why. You are not making bad picks. You are paying a 30% tax on every dollar before your edge, if any, gets to express itself. A 55% win rate on game lines might generate real profit. A 55% "hit rate" on Super Bowl futures, picking winners at long prices, still loses money when the overround is 130%.
The only futures bet that beats the overround structurally is one where you have information the market hasn't priced yet, or where you find a team at one book priced 25%+ better than the consensus. Everything else is paying a tax. Know the tax before you pay it.
Citations
- Harville, D.A. (1973). "Assigning Probabilities to the Outcomes of Multi-Entry Competitions." Journal of the American Statistical Association, Vol 68, No 342, pp 312-316. Tandfonline
- Thaler, R.H., and Ziemba, W.T. (1988). "Anomalies: Parimutuel Betting Markets: Racetracks and Lotteries." Journal of Economic Perspectives, Vol 2, No 2, pp 161-174. AEA
- Hegarty, M., and Whelan, K. (2025). "Estimating Expected Loss Rates in Betting Markets: Theory and Evidence." Applied Economics. Tandfonline
- Whelan, K. (2025). "Market Structure and Prices in Online Betting Markets: Theory and Evidence." Oxford Economic Papers. Oxford Academic
- RG.org. (2026). "U.S. Sports Betting Statistics September 2026: Handle, Revenue and Tax." RG.org
- DraftKings Sportsbook. (September 2026). NFL Super Bowl Futures odds board. DraftKings
- Vegas Insider. (September 2026). NFL Futures odds board: 2026-27 Super Bowl odds. Vegas Insider