Arbitrage Calculator

What is arbitrage betting?

Arbitrage betting (also called "arbing" or "sure bets") is the practice of placing simultaneous wagers on all possible outcomes of a market at prices that guarantee a profit regardless of how it resolves. It's only possible when different sportsbooks disagree enough on a line that their combined prices imply less than 100% total probability.

The math is straightforward. If Book 1 has Team A at +110 and Book 2 has Team B at -100, the implied probabilities are 47.62% and 50.00%, totaling 97.62%. That's a 2.38% arb margin. Stake your total wager proportionally across both sides and the return is the same no matter which side wins, giving you a guaranteed profit.

Why arbs exist

Sportsbooks price lines based on their own models, the betting action they're seeing, and the margin they want to earn. Different books have different models, different user bases, and different tolerances for exposure on a given market. When those factors push lines in different directions, a cross-book arb can open up. It usually closes quickly as the books adjust.

Arb margins on US sports are typically small, often well under 3%. Live in-play markets and niche sports produce larger arbs more frequently because the lines move faster and sharper bettors are slower to hit them. Futures markets can produce larger but harder-to-execute arbs because they don't resolve for months.

Why arbitrage is harder than it sounds

On paper, an arb is a risk-free profit. In practice, there are real obstacles:

• Account limits. Sportsbooks actively identify arbers and limit or ban their accounts. If you're noticed, your stake sizes get cut to amounts where the arb isn't worth executing.
• Line movement. By the time you've placed the first leg, the second leg may have moved, turning your sure thing into a middled position or an outright loss.
• Rejected bets. A book can cancel or void your wager after you've placed the other leg, leaving you exposed on one side.
• Bonus restrictions. Bonus funds often have max-bet limits or can't be used on both sides of a market, limiting arb size.
• Capital efficiency. Arb margins are small. Making meaningful money from arbing requires large bankrolls split across many sportsbook accounts, which is operationally expensive.

Arbs vs middles vs value bets

A true arbitrage locks in profit on every possible outcome. A middle is similar but usually refers to spread or total markets where, if the result lands in a specific range between the two lines you bet, both sides win. A value bet is a single-leg wager on one side at a price better than the fair no-vig price, which has positive expected value but isn't guaranteed to win. Value betting is the broader and more sustainable activity for most bettors.

Related reading

The hedging and middling guide covers the related techniques in depth. The line shopping guide explains why cross-book pricing differences exist in the first place. The no-vig calculator helps evaluate single-side value bets.