An arbitrage bet finder scans the prices of many bookmakers on the same market and flags any case where backing every outcome, each at a different bookmaker, costs less than it returns. It does the maths for you: the arb percentage and the stake for each side. What it can't do is promise the arb still exists when you place your bet, or that both bookmakers will settle the market the same way. Treat every flagged arb as a candidate, then run the checks below before the second leg goes on.
How an arbitrage bet finder works
Every finder does the same four jobs, just at different speeds and across different numbers of bookmakers.
- Collects prices. It pulls odds for the same event and market from each bookmaker it covers.
- Takes the best price per outcome. For a two-way market, that's the best price on each side, usually from two different bookmakers.
- Adds up the implied probabilities. Each decimal price converts to a probability with 1 ÷ odds. If the total across all outcomes is under 100%, the market is an arb (Wikipedia: Arbitrage betting).
- Splits your stake. It divides your total outlay so each outcome returns roughly the same amount.
BetBank's arbitrage finder does this across Australian bookmakers and shows the stake for each side at current prices. If you want the full theory first, our guide on how arbitrage betting works covers the formula and where arbs come from.
A worked example (invented numbers)
Say a finder flags an NBA head-to-head market. NBA games can't end in a draw because tied games go to overtime (NBA Official Rulebook), so it's a clean two-way market.
| Bookmaker A | Bookmaker B | |
|---|---|---|
| Team X | 2.10 | 1.95 |
| Team Y | 1.85 | 2.00 |
The finder takes Team X at 2.10 (Bookmaker A) and Team Y at 2.00 (Bookmaker B).
- Team X: 1 ÷ 2.10 = 47.62%
- Team Y: 1 ÷ 2.00 = 50.00%
- Total: 97.62%, so the margin is 1 ÷ 0.9762 minus 1 = 2.44%
On a $500 total outlay, the stakes are:
| Bet | Stake | Return if it wins |
|---|---|---|
| Team X at 2.10 | $243.90 | $512.19 |
| Team Y at 2.00 | $256.10 | $512.20 |
Whichever team wins, you get back about $512.20 on $500, a profit of about $12.20. That's the number a finder shows you. The rest of this post is about why the number you actually end up with can be different.
Check 1: is the price still there?
Prices move all the time, and a finder only sees them as often as it refreshes. Most arbs are small: Wikipedia notes that about 98% of arbitrage opportunities return under 1.2% (Wikipedia: Arbitrage betting). A small margin doesn't take much movement to disappear.
Here's what happens if Team Y drops from 2.00 to 1.90 after you've already placed the Team X bet.
- New total: 47.62% + 52.63% = 100.25%. The arb is gone.
- To make both outcomes return the same $512.19, you now need $269.57 on Team Y at 1.90.
- Total outlay: $243.90 + $269.57 = $513.47, for a return of $512.19. A loss of about $1.28 either way.
That's the better outcome. The worse one is leaving the first bet unhedged and being fully exposed on one side.
What to do: open both bets before confirming either. Place the leg most likely to move first (usually the bookmaker whose price is out of line with the market), then confirm the second price before you commit the stake.
Check 2: do both bookmakers settle the market the same way?
This is the check most finders don't do for you, and it's where a neat-looking arb loses a whole leg. Two bookmakers can list what looks like the same market and settle it under different rules.
Tennis retirements
There's no single Australian rule for a player retiring mid-match. According to Before You Bet:
| Bookmaker | If a player retires after the first set |
|---|---|
| Ladbrokes, PalmerBet, Unibet | The retiring player loses, bets on the opponent are paid |
| Sportsbet | Refund if your player retires; paid if the opponent retires after set one |
| bet365, TAB | All bets void and refunded, whoever retires |
Now picture an arb with Player A at a bookmaker that settles retirements after the first set, and Player B at one that voids all retirements. If Player A retires after the first set, your Player A bet loses and your Player B bet is refunded. You've lost the Player A stake with nothing to offset it.
NBA markets and overtime
A standard two-way NBA head-to-head includes overtime. A three-way market that quotes a price on a draw is settled at the end of regulation time, so a draw is a real result. Pairing a two-way price from one bookmaker with a three-way price from another isn't an arb at all, even if the numbers look like one.
Player props and players who don't play
NBA player props (points, rebounds, assists, threes) are usually void if the player doesn't take the court, but the details vary: some bookmakers settle on whether the player started, others on whether the player logged any minutes. With the 2026-27 NBA season starting on 20 October (FOX Sports), late scratches and minutes limits will come up every week. If one side of a prop arb is void and the other stands, you're no longer arbing.
What to do: before the first bet, open each bookmaker's rules for that sport and market type. If you can't confirm the rules match, skip the arb.
Check 3: will both bookmakers take your full stake?
The stake split only works if both bets go on at the size the finder suggests. A bookmaker may accept a smaller stake than you asked for, which leaves the other side over-staked. Bookmakers also watch for arbitrage: accounts that arb often see their maximum stakes cut heavily, often to the point where arbing isn't viable (Wikipedia: Arbitrage betting).
Rounding matters too. If you round the example stakes to $244 and $256 to look less like an arber, you'd get back $512.40 if Team X wins and $512.00 if Team Y wins. That's fine at a 2.44% margin. At 0.5%, rounding can take most of it.
What to do: place the leg with the lower likely limit first. If it's only partly accepted, resize the second leg to match before you place it.
Check 4: does commission or a fee change the maths?
If one leg is on a betting exchange, commission comes off your net winnings, so the price you see isn't the price you get. Betfair Australia's market base rate on sport went up from 5% to 6% on 25 March 2025, with NRL markets at 10% (The Straight).
Rework the example with Team X backed on the exchange at 2.10 instead of a bookmaker:
- Effective price after 6% commission: 1 + (1.10 × 0.94) = 2.034
- New total: 49.16% + 50.00% = 99.16%
- New margin: 0.84%, down from 2.44%
Most of the edge is gone before the price has moved at all. A good finder lets you enter commission so the arb percentage it shows is the one you'll actually get.
Check 5: is the arb real, or an error?
A very large arb usually means one price is wrong: a typo, a stale line or a market that settles differently. Bookmakers can void bets struck at obviously wrong prices, which leaves the other leg standing on its own. When a finder shows a margin far above the small ones most arbs carry, look for the reason before you bet.
Pre-match only: the Australian in-play rule
Many overseas guides talk about live arbs. In Australia, the Interactive Gambling Act bans online in-play betting on sport with licensed operators, except bets placed wholly over the phone (Mediaweek). So for bettors using Australian-licensed bookmakers, arbing is a pre-match activity. Stick to bookmakers licensed in Australia: an arb that needs an unlicensed site to work isn't one worth taking.
What to look for in an arbitrage bet finder
| Feature | Why it matters |
|---|---|
| Refresh speed | Slower feeds show more arbs that have already gone |
| Bookmaker coverage | More Australian bookmakers means more real candidates |
| Market matching | It should only pair markets with the same settlement terms |
| Commission settings | So exchange legs show their true margin |
| Stake calculator | Exact stakes per side, ideally with a rounding option |
| Bet tracking | So you can compare the margin you were shown with what you actually got |
Free finders are useful for learning the maths. Before paying for any finder, check the first three rows: they decide how many flagged arbs survive the checks above. You can also cross-check any flagged price yourself on BetBank's odds screen, and log every arb you place so you can see your real margin against the one you were shown.
Try it on the NBA board this season
BetBank's arbitrage finder, positive EV tools and line movement are in the Gold plan, alongside the NBA odds board and player props. For the NBA season, first-time members on a weekly or monthly plan pay half price for their first 2 months, after a 7-day free trial, if they start by 30 November 2026. See the details on the BetBank NBA season page, then run every flagged arb through the five checks before you bet.
Arbitrage is not a way to make money without risk: prices move, rules differ and accounts get limited. Only bet what you can afford to lose. If gambling stops being fun, you can block yourself from all licensed Australian online and phone gambling with BetStop. You must be 18+ to bet. Please gamble responsibly.