What Is Arbitrage Betting in the NFL?

Key takeaways

• Definition: arbitrage betting means backing every outcome of the same NFL market at different sportsbooks or prediction markets, at prices that return more than the total staked whichever side wins.

• The test: convert each price to an implied probability and add them up. A sum under 100% is an arb. A Bills -150 moneyline (60%) against a 38-cent Dolphins contract (38%) sums to 98%, so it’s a 2.04% return.

• Vig and fees: two -110 prices add up to 104.76%, so two sportsbooks have to disagree by more than 4.76 points before an arb appears. Novig charges no fee on pre-game straight trades, which cuts that gap to 2.38 points against a -110 book.

• Risks: if one leg is voided, limited or repriced before the other is placed, what’s left is a one-sided bet. Ties and voids can also settle differently on each platform.

• Legality: each leg is an ordinary bet or trade, legal wherever that operator is legal for the bettor. Sportsbook house rules let books limit or refuse wagers.

What arbitrage betting is

Arbitrage betting, or arbing, is placing bets on every side of the same market at two or more places, sized so the payout is the same whichever side wins. When the prices are far enough apart, that payout is larger than the total staked, and the difference is profit. Nobody’s picking a winner.

In the NFL, an arb is almost always two legs: both moneylines, both sides of a spread, or the over and under of a total. The legs have to be the same market at the same number. Bills -2.5 at one book and Dolphins +3.5 at another make a middle, which wins both bets if the Bills win by exactly three and otherwise wins one bet and loses the other.

How an NFL moneyline arb works

Start by converting each price to an implied probability: odds / (odds + 100) for minus odds and 100 / (odds + 100) for plus odds, sign dropped. A prediction-market contract’s price in cents is already the probability. The moneyline explainer has the full conversions.

Take a hypothetical Bills-Dolphins game. A sportsbook has the Bills at -150, which implies 60%. On a prediction market, the Dolphins contract trades at 38 cents, or 38%. Together that’s 98%, so the pair is an arb, and the return is 1 / 0.98 - 1, or 2.04% of the money staked.

Each leg is sized to return the same amount. For a $1,000 payout, the book stake is $1,000 divided by 1.667, the decimal price of -150, and the other leg is 1,000 contracts at 38 cents:

Either team winning returns $1,000 on $980 staked, a $20 profit. If the Dolphins leg is a pre-game trade on Novig, the $380 is the whole cost of that leg, since Novig doesn’t charge a fee on pre-game straight trades.

A spread arb across a sportsbook and a prediction market

Spreads work the same way as long as both legs sit on the same number. Say the book has Bills -2.5 at -110 (52.38%) and a prediction market has the Dolphins +2.5 contract at 45 cents (45%). The sum is 97.38%, a return of 2.69%.

For a $1,000 payout, the book leg takes $523.81 ($1,000 divided by 1.9091, the decimal price of -110) and the prediction-market leg takes 1,000 contracts at 45 cents, or $450. That’s $973.81 staked to get back $1,000, a $26.19 profit. A Bills win by three or more cashes the book bet, and any other result cashes the contract. The half point rules out a push on either leg. How hooks and key numbers affect a line is covered in what a point spread is.

Why arbitrage opportunities exist

Every sportsbook sets and moves its own lines. Some react first to injury news or large bets and others follow minutes later, and books with different customers shade the same game in different directions. For a short window, the best price on each side sits at a different book.

Prediction markets add another source of disagreement. Their prices come from orders placed by traders instead of a book’s oddsmakers, so a contract can sit a few cents away from where the books are dealing the same game. The gaps don’t last, which is why arbitrage bettors watch many books at once with odds comparison sites and dedicated arbitrage betting tools.

How vig and fees shrink an arb

A sportsbook’s margin is built into both of its prices. Two sides at -110 imply 52.38% each, or 104.76% in total, so a book holding equal money on both keeps 4.55% of what’s wagered. Two -110 books can’t produce an arb unless their prices disagree by more than that 4.76-point overround.

A trade that doesn’t carry a fee removes half of that gap. Novig doesn’t charge a fee on pre-game straight trades, and the maker on any trade pays nothing, according to its fee schedule. A -110 side paired with a fair 50-cent contract sums to 102.38%, so the two only need to disagree by 2.38 points.

Fees come back on live trades, where a Novig taker on an NFL market pays 0.03 x price x (1 - price) per contract. Take an Over 47.5 at -110 at a book and an Under 47.5 contract at 47 cents, about +113 in American odds. Before kickoff that pair sums to 99.38%: $523.81 plus $470 returns $1,000, a $6.19 profit. Taken live at the same prices, the Under costs about $0.0075 more per contract, or $7.47 on 1,000 contracts, and the position loses $1.28. A resting order at 47 cents that another trader fills carries no fee, but there’s no guarantee it fills before the price moves.

Risks that can break an arb

The math doesn’t hold unless both legs are placed at the prices shown and graded the way the bettor expects.

Voided bets and palps

Sportsbook house rules let a book void a bet placed at an obvious pricing error, often called a palp. If one leg of an arb is voided and the other stands, what’s left is an ordinary one-sided bet. WCPO reported that Ohio sportsbooks voided $77 million in bets over the 13 months through Jan. 30, 2024, 0.91% of the $8.5 billion wagered. A gaming-compliance executive quoted in the same report said Massachusetts, Pennsylvania and New Jersey require sportsbooks to get approval before they void bets.

Stake limits

Books can cap what a customer’s allowed to bet. FanDuel’s West Virginia house rules reserve the right “at its sole discretion, to refuse, limit or cancel any wager or series of wagers.” On a prediction market the other side of a trade is another user, and the constraint is order-book depth: only the size resting at the quoted price fills there, and anything beyond that fills at worse prices.

Prices that move before both legs fill

The two bets don’t go in at the same moment, and prices can move in between. If the Dolphins contract goes from 38 to 42 cents after the Bills bet is placed, the pair sums to 102%, and the position loses $20 whichever team wins. Placing the leg most likely to move or be refused first limits the exposure.

Settlement rules that differ

Each platform grades the same game under its own rules, and they don’t always match. A regular-season NFL game still level after one 10-minute overtime period ends in a tie. On a two-way sportsbook moneyline that’s a push, and the stake comes back. Novig’s NFL winner contracts pay 50 cents per contract to each side on a tie. In the moneyline example, a tie returns the $600 book stake plus $500 from 1,000 contracts, $1,100 on $980. With the legs flipped, the Bills at 60 cents on the prediction market and the Dolphins at +163 at the book, a tie returns $880.23 on $980.23, a $100 loss.

Full-game NFL markets generally count overtime, but some totals and segment markets on both kinds of platform cover regulation only. A sportsbook typically refunds a voided bet, while Novig settles a voided contract at a fair value price taken from trading just before the disruption, which can be more or less than what was paid.

Is arbitrage betting legal?

Each leg of an arb is an ordinary wager or trade, and it’s legal wherever that sportsbook or prediction market is legal for the bettor to use. Sportsbooks are licensed state by state, and several states are contesting whether prediction markets can offer sports contracts, so the available legs depend on location. The guide to prediction markets vs. sportsbooks covers how each is regulated.

House rules like the FanDuel one quoted above let a sportsbook limit stakes or refuse wagers from any customer at its discretion, and that includes customers who arb.

Arbitrage betting FAQ

How much does an NFL arb usually return?

Not much per bet. The examples here return 0.62% to 2.69% of the money staked. That’s about $6 to $26 for every $1,000 paid out.

Is arbitrage betting risk-free?

No. The return’s fixed once both legs are placed at the prices shown, but a voided leg, a partial fill, a moved price or a settlement difference on a tie can each leave a loss.

How do you calculate arbitrage stakes?

Pick a target payout and divide it by each sportsbook leg’s decimal odds. For a prediction-market leg, buy as many contracts as the payout in dollars. When the prices form an arb, the stakes add up to less than the payout.

Can you arb a sportsbook against a prediction market?

Yes, as long as both legs are the same market at the same number and both platforms are legal where you are. Add the contract price in cents to the book’s implied probability.

What’s the difference between an arb and a middle?

An arb takes both sides at the same number and returns the same amount either way. A middle takes the two sides at different numbers, such as Bills -2.5 and Dolphins +3.5, and wins both bets only if the margin lands between them.