Arbitrage Calculator

How to use it

1. 1 Pick your odds format and choose two-way (for example a spread or moneyline) or three-way (win, draw, lose).
2. 2 Type the best available odds for each outcome, usually from different sportsbooks.
3. 3 Enter the total amount you want to spend across all outcomes.
4. 4 Read the stake for each outcome, the equal return, the profit and the ROI. If the result is negative, there is no arbitrage at those odds.
5. 5 Optionally round the stakes to the nearest $1 or $5 to see what you make on each outcome with realistic bet sizes.

What an arbitrage bet is

An arbitrage (or "arb") is a set of bets on every possible outcome of one event, placed at prices good enough that the total payout is more than the total stake whichever outcome wins, as long as every bet is accepted at those prices. It happens when different sportsbooks disagree about the same event.

The test is the implied probability of each price, which is 1 divided by the decimal odds. If the implied probabilities across all outcomes add up to less than 100%, an arbitrage exists. If they add up to 100% or more, it does not.

How the stakes are calculated

Each outcome gets a share of your total stake in proportion to its implied probability. That makes every outcome return the same amount, so you do not need to know who wins.

The equal return is the total stake divided by the sum of the implied probabilities. Profit is that return minus the total stake, and ROI is profit divided by the total stake.

Worked example

Sportsbook 1 offers +110 on Outcome A and sportsbook 2 offers +110 on Outcome B. In decimal that is 2.10 each, so each implied probability is 47.62% and they add up to 95.24%.

With a $1,000 total stake, you put $500.00 on each side. Whichever side wins, it returns $1,050.00, a profit of $50.00, which is a 5.00% ROI.

Compare a market with -110 on both sides. The implied probabilities add up to 104.76% (an overround of 4.76%), so a $1,000 total stake returns $954.55 whichever side wins, a loss of $45.45. That loss is 4.55% of the money staked, which is the hold on that market, and the calculator shows it rather than hiding it.

Why rounding matters

Sportsbooks do accept cent stakes, but round stakes such as whole dollars or $5 look less like arbitrage betting than $47.62 does, so many people round. When you round, the return is no longer identical on every outcome, and one side may pay less than the other. For example, at +120 and +100 with $100 total, the exact stakes are $47.62 and $52.38. Rounding to $5 gives $50 and $50, which pays $10.00 if the +120 side wins and $0.00 if the +100 side wins.

Use the rounding option to check that the weakest outcome is still acceptable before you place the bets.

Risks that the maths does not cover

The profit is locked in only if both bets are accepted at these odds. Odds move, limits cut stakes, and a bet can be voided or settled differently by each book (for example on a postponed game or a push). Check the rules for both bets before you commit.

Members can see live arbitrage opportunities across sportsbooks on the TheOver.ai arbitrage page.

The formula

Frequently asked questions