What is arbitrage betting?

Betting all possible outcomes of the same event across different sportsbooks at prices where the implied probabilities add up to less than 100%, so the combined stakes return a profit no matter which outcome happens.

Is arbitrage betting guaranteed profit?

Only in theory, if both legs are placed at the quoted prices before either one moves. In practice a price can change between your two bets, a book can limit or void a bet, and account restrictions can shut off the strategy entirely.

How do sportsbooks respond to arbitrage bettors?

Many books track betting patterns and limit, restrict, or close accounts that consistently bet both sides of markets for arbitrage, which is why the opportunity can disappear even after you have found it.

How do I calculate the stake split for an arbitrage bet?

Each side’s stake is your total stake times that side’s implied probability divided by the sum of both implied probabilities. TheRundown’s arbitrage calculator does this automatically.

Where can I find arbitrage opportunities on TheRundown?

The odds board highlights arbitrage opportunities in gold, and HedgeMaker scans across sportsbooks specifically to find them.

What happens if one leg of an arbitrage bet gets voided?

A voided or palpable-error ruling on one leg turns a theoretically risk-free pair of bets into a single, unhedged bet, which can result in a real loss rather than a guaranteed profit.

Arbitrage betting: how it works, with the math

Arbitrage betting means placing a bet on every possible outcome of the same event at different sportsbooks, at prices where the combined implied probabilities add up to less than 100%. When that happens, the payout from whichever outcome wins covers all your stakes and still leaves a profit, regardless of the result. It depends entirely on finding mispriced lines before they move or get limited, so it is less a betting strategy than a pricing exercise with real execution risk attached.

What an arbitrage bet actually is

A sportsbook’s price on a two-way market (say, a moneyline) reflects an implied probability for each side. If you could bet both sides of the same market at the same book, the two implied probabilities would add up to more than 100% — that gap is the book’s margin, or vig. An arbitrage, or “arb,” exists when you bet the two sides at two different books, and the book offering each side happens to have priced it generously enough that the two implied probabilities add up to less than 100%. The difference is locked in as profit, split proportionally across both stakes.

The math: implied probability and the sum

Two conversions do all the work:

American to decimal odds

Positive American odds: decimal = 1 + (american / 100)
Negative American odds: decimal = 1 + (100 / |american|)

Decimal odds to implied probability

implied probability = 1 / decimal

An arbitrage exists when the implied probabilities of the two (or more) sides, taken from their best available prices across different books, sum to less than 1:

implied_A + implied_B < 1

When that is true, the profit percentage and each side’s stake are:

profit % = (1 / (implied_A + implied_B) − 1) × 100
stake_A  = total_stake × implied_A / (implied_A + implied_B)
stake_B  = total_stake × implied_B / (implied_A + implied_B)

Stakes are split proportionally to implied probability so that the payout is the same no matter which side wins.

Example: working the numbers

Suppose Book A has Team X at +150 and Book B has Team Y, the only other outcome in the same market, at −120. These are hypothetical prices for illustration only.

Step 1 — convert to decimal odds

Team X: +150 → 1 + 150/100 = 2.50
Team Y: −120 → 1 + 100/120 = 1.83333…

Step 2 — implied probability

Team X: 1 / 2.50 = 0.40000 → 40.00%
Team Y: 1 / 1.83333… = 0.54545 → 54.55%

Step 3 — sum the implied probabilities

0.40000 + 0.54545 = 0.94545  (94.55%)

Because the sum is below 1, this is an arbitrage.

Step 4 — profit percentage

(1 / 0.94545 − 1) × 100 = 5.77%

Step 5 — stake split on a $1,000 total

stake_X = 1,000 × 0.40000 / 0.94545 = $423.08
stake_Y = 1,000 × 0.54545 / 0.94545 = $576.92

Step 6 — check the payout either way

If Team X wins: $423.08 × 2.50 = $1,057.70
If Team Y wins: $576.92 × 1.83333… = $1,057.69

Both outcomes return about $1,057.69 on a $1,000 outlay (rounding the stakes to the cent moves one leg by a penny): a profit of about $57.69, or 5.77%, locked in before the game is played. The two payouts matching is the check that the stake split is right.

Why arbitrage opportunities exist, and why they disappear

Sportsbooks price independently, using their own models and their own view of which side needs incentive to balance their liability. Early lines, injury news, and lopsided public betting all push one book’s price away from another’s faster than the market as a whole can correct. That gap is the arbitrage window.

It closes quickly. Other bettors and automated tools hunt for the same mispricing, and sportsbooks’ own risk systems move a line as soon as one side takes too much action. A price you see is not a price you are guaranteed to get by the time you place the second leg.

The real risks

Arbitrage is often described as risk-free, but that only holds if everything executes exactly as planned. In practice:

Limits. Sportsbooks can and do limit or restrict accounts that repeatedly bet both sides of a market, which is a hallmark pattern of arbitrage. A limited account may no longer get the prices that make the strategy work.
Voided or palpable-error bets. If a book rules a price a palpable error, or voids a bet for another reason, you can be left holding only one leg of what was supposed to be a hedged pair. If that leg loses, you lose its stake instead of locking in a profit.
The second leg can move before you place it. Prices change in seconds. If the second book’s price moves after you have already placed the first leg, the sum of implied probabilities can rise back above 100% before you get your bet in, erasing the edge or turning it into a loss.
Account restrictions over time. Beyond a single limited bet, some books restrict or close accounts entirely once a pattern of arbitrage-style betting is identified, which affects your ability to use that book going forward.
Variance returns the moment the hedge breaks. The entire appeal of arbitrage is that it removes variance by covering every outcome. Any one of the failures above — a limit, a void, a late price move — can leave you holding a single, unhedged bet, which puts you right back under the normal variance of a one-sided wager.

None of this is a reason to assume arbitrage never works — it describes why it is a pricing-and-execution exercise, not a guaranteed profit machine, and why position sizing and speed matter.

How to find arbitrage opportunities on TheRundown

The odds board compares every book’s price for a market side by side and highlights arbitrage opportunities in gold. Check any board, such as the NFL odds or NBA odds.
HedgeMaker scans across sportsbooks specifically to find arbitrage opportunities, rather than requiring you to scan a full board yourself.
The arbitrage calculator takes the prices you have found and does the implied-probability, profit-percentage, and stake-split math shown above for you, so you can verify an opportunity before you bet it.

21+. If you or someone you know has a gambling problem, call 1-800-GAMBLER.

Questions

What is arbitrage betting?: Betting all possible outcomes of the same event across different sportsbooks at prices where the implied probabilities add up to less than 100%, so the combined stakes return a profit no matter which outcome happens.
Is arbitrage betting guaranteed profit?: Only in theory, if both legs are placed at the quoted prices before either one moves. In practice a price can change between your two bets, a book can limit or void a bet, and account restrictions can shut off the strategy entirely.
How do sportsbooks respond to arbitrage bettors?: Many books track betting patterns and limit, restrict, or close accounts that consistently bet both sides of markets for arbitrage, which is why the opportunity can disappear even after you have found it.
How do I calculate the stake split for an arbitrage bet?: Each side’s stake is your total stake times that side’s implied probability divided by the sum of both implied probabilities. TheRundown’s arbitrage calculator does this automatically.
Where can I find arbitrage opportunities on TheRundown?: The odds board highlights arbitrage opportunities in gold, and HedgeMaker scans across sportsbooks specifically to find them.
What happens if one leg of an arbitrage bet gets voided?: A voided or palpable-error ruling on one leg turns a theoretically risk-free pair of bets into a single, unhedged bet, which can result in a real loss rather than a guaranteed profit.

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