Arbitrage / Field Bet Calculator

What is Arbitrage Betting?

Arbitrage (often called "arb" or "sure bet") occurs when you can place bets across all possible outcomes of an event at odds where every outcome is profitable. This creates a risk-free situation where you're guaranteed to make money regardless of which outcome occurs.

Arbitrage opportunities typically arise due to differences in odds between sportsbooks, movements in odds over time, or in field bets where the probability implied by all odds doesn't sum to 100%. Sharp bettors and syndicates constantly hunt for arbitrage, which is why opportunities close quickly when detected.

The key number to watch is the implied probability sum. If the implied probabilities of all outcomes add up to less than 100%, an arbitrage exists. The further below 100%, the more profit you can lock in. This calculator shows you that number in real time as you enter odds.

When Does Arbitrage Appear?

Cross-book arbitrage: Different sportsbooks price the same event differently. Book A has Team A at +150 while Book B has Team B at +120. If the implied probabilities from the best available odds on each side sum to less than 100%, you have an arb. This is the most common type and the one professional arb traders focus on.

Field bets and futures: A sportsbook offers "Win the Super Bowl" odds for individual teams, with remaining teams lumped into a "Field" option. By combining bets on individual teams across different books, you can sometimes cover every outcome profitably. This calculator supports up to 12 outcomes for exactly this scenario.

Live and in-play arbitrage: Odds shift rapidly during live events. A goal, injury, or momentum swing can create momentary discrepancies between books that haven't adjusted yet. Speed is everything here — these windows close in seconds.

Prediction market arbitrage: Platforms like Polymarket, Kalshi, and PredictIt sometimes price the same event differently. Because these are exchange-based markets with different liquidity profiles, price discrepancies can persist longer than in traditional sportsbooks.

How to Use This Calculator

Step 1: Enter the odds for each outcome you're considering. Toggle between moneyline, decimal, or prediction market pricing — the calculator converts automatically. Name each outcome so you can keep track.

Step 2: Check the implied probability sum. If it's below 100%, an arbitrage opportunity exists at these odds. The "Your Edge" stat shows how much room you have to work with.

Step 3: Enter your bet amounts. The calculator shows your profit/loss for every possible outcome. Use the "Optimal Bet Sizing" section to see how to split your total wager for equal profit across all outcomes.

Step 4: Verify that every outcome shows a positive profit. If even one is negative, you're not fully hedged. Adjust your bet sizing or look for better odds.

The "All other outcomes" row at the bottom shows what happens if none of your named outcomes wins — this is your total loss in that scenario. In a true arbitrage where you've covered every possible outcome, this row should never trigger.

Why Is Arbitrage Temporary?

Sportsbooks employ automated odds-adjustment systems and monitor the market 24/7. The moment an arbitrage is detected — either by sharp traders or by competing books — odds will shift to close the gap. Large or obvious arbitrage opportunities rarely last more than minutes. This is why professionals use specialized software to spot and execute arbs at scale.

Additionally, many modern sportsbooks now limit or restrict winners, meaning sustained arbitrage play can get your account closed or limits reduced. Some arb traders use multiple accounts, but this carries its own risks. The most sustainable approach is to combine arbitrage with other strategies like value betting and line shopping.

Arbitrage vs. Hedging vs. Parlay Betting

Arbitrage means covering every possible outcome simultaneously at odds that guarantee profit. You need different odds sources (typically different sportsbooks) and you place all bets before the event starts or during live play.

Hedging is similar but happens sequentially: you placed an original bet, and now you're betting the other side to lock in profit. Use our Hedge Calculator for that scenario.

Parlay betting is the opposite of both. In a parlay, you're stacking multiple bets together and need all of them to win. You're taking on more risk for a bigger payout. Arbitrage requires no luck — it's pure mathematics.

Who Uses Arbitrage Calculators?

Professional arb traders who scan dozens of sportsbooks for pricing discrepancies and execute quickly before odds move. They typically target 1-3% guaranteed returns per arb.

Prediction market traders comparing prices across platforms like Polymarket, Kalshi, and PredictIt to exploit price differences on the same events.

Matched bettors using sign-up bonuses and free bets from sportsbooks. By combining a free bet with an opposing real-money bet, you can extract guaranteed value from promotions.

Curious bettors who want to understand how the math works, even if they're not executing arbs. Understanding implied probability sums helps you recognize when a book is offering unusually good or bad odds.