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What an arbitrage is
An arbitrage ("arb") is a set of bets on every outcome of a market, at different books, where the prices disagree enough that the right stakes return the same amount whichever side wins, and that amount is more than you staked. It happens when the books' implied probabilities for the best price on each side add up to less than 1.
Live The Arbitrage screen finds arbs at the books you pick, on net prices after fees: 2-way and 3-way (including the draw), and across different points on alt-line ladders. It runs in your browser, so changing the Book: selector re-prices it immediately. The Home dashboard's Best arbitrage card shows the top one at default settings, and the arbitrage calculator does the same stake math for any prices you enter.
The math
Booksum S = Σ 1 ÷ dᵢ over the best net decimal on each outcome
Arb if S < 1; locked return = 1 ÷ S − 1
Stake on outcome i for a total T: sᵢ = T × (1 ÷ dᵢ) ÷ S, so every outcome returns T ÷ S
Worked example
Team A is +108 at FanDuel and Team B is −102 at BetMGM. For a $100 total:
Decimals: +108 → 2.0800; −102 → 1.9804
S = 1 ÷ 2.0800 + 1 ÷ 1.9804 = 0.48077 + 0.50495 = 0.98572
Return = 1 ÷ 0.98572 − 1 = +1.45%
Stakes: $48.77 on A, $51.23 on B; either way the payout is $101.45, a $1.45 profit
Now put the +108 on ProphetX instead, which charges 2% of net winnings. The net decimal is 1 + 1.08 × 0.98 = 2.0584 (about +106):
S = 1 ÷ 2.0584 + 1 ÷ 1.9804 = 0.99076
Return = +0.93%; stakes $49.03 / $50.97; payout $100.93
The fee took a third of the arb. That is why every price on the site is compared at its net price: an arb that only exists before fees isn't an arb.
Second example: a 3-way soccer arb and rounded stakes
A soccer match: Home +150 at one book, Draw +260 at a second, Away +240 at a third. Every outcome needs a leg.
S = 1 ÷ 2.50 + 1 ÷ 3.60 + 1 ÷ 3.40 = 0.4000 + 0.2778 + 0.2941 = 0.9719
Return = 1 ÷ 0.9719 − 1 = +2.89%
Stakes for $100: $41.16 / $28.58 / $30.26 → $102.89 whichever outcome wins
Books don't like odd cents, and stakes like $41.16 can draw attention. Rounding to whole dollars ($41 / $29 / $30) keeps the arb but makes the profit uneven: $2.50 if Home wins, $4.40 on a Draw, $2.00 if Away wins. Rounding is fine as long as you check that every outcome stays positive. On a thinner arb, rounding can push one outcome below zero.
Make sure all three legs are the regulation-time 1X2 market. A moneyline that includes extra time or penalties settles differently from a 90-minute result.
How to read the screen
The top bar holds the Book: selector, a league menu, a market menu (All markets, Game lines, Player props, Alt lines), a minimum-profit menu (Any profit, Profit ≥ 1% and so on), search (press /) and your Target bet, saved on this device. Each row, column by column:
| Column | What it shows |
|---|---|
| ARB % | The locked return, 1 ÷ S − 1, after fees. A + middle tag means the legs sit at different points and both can win if the result lands between them. Sortable. |
| EVENT | Start time, matchup and league. Sort by it to see the soonest games first. |
| MARKET | The market, an alt badge for alternate points, and a same venue warning when both legs sit in one exchange family (usually not placeable together). |
| BOOKS | One line per leg: selection, net price (marked net for exchanges), Liq $ where we hold the exchange's order book, the book, +N when other books have the same price, and a link to the book's site (offshore books are odds only and never linked). |
| BET SIZE | An editable stake per leg, split from your target and rounded to $1 by default (change rounds to the cent or $5). Edit one leg and the others rescale to keep the payout equal. |
| PROFIT | The worst-case profit on those stakes and its ROI, or not fillable when a leg has no liquidity. |
The chevron expands OUTCOMES (what each result returns and nets) and STAKES (each book's share of the total). Clicking a row opens the stake calculator: total stake, Exact / $1 / $5 rounding, Copy stakes, each leg's price age against what its refresh tier allows, a warning when liquidity caps the fill, and the math. The eye icon hides a row on this device.
Two rules keep the list honest. An arb is shown only while every leg is younger than twice the refresh interval that applies to it; older ones are counted as stale hidden. And where an exchange's order book shows $0 at the price, that leg is sized at 0 instead of pretending the arb fills. Pick'em apps and thin exchange quotes never form an arb.
When nothing crosses, the screen says No arbs open at your books. That is normal: arbs appear and vanish within minutes, and most of the time there aren't many. Switching the Book: selector to All books shows more.
Pitfalls
- Stale lines. Most arbs are one book that hasn't moved. They appear and vanish within minutes, and our prices refresh on a schedule (every minute for game lines in the last 2 hours, less often further out). Confirm both prices before you place either leg.
- Leg risk. If the second price moves after you place the first, you hold an unhedged bet. Place the leg most likely to move first.
- Limits and voids. A book can limit the stake or void a bet it considers a palpable error, leaving you one-sided. Sharp-looking patterns can also get accounts limited.
- Thin exchange markets. The quoted exchange price may only be good for a few dollars.
- Rules mismatches. Make sure both legs settle the same way (overtime included or not, regulation 1X2 versus moneyline, player-did-not-play rules).
Open the tool
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