Arbitrage step-by-step — your first $10 arb

Arbitrage is the only kind of bet where you can win money no matter who wins the game. It works because different sportsbooks price the same event slightly differently, and when those differences are big enough, you can bet both sides at both books and fix a profit on both sides.

This lesson walks you through your first one, with real numbers.

What an arb actually is

An "arbitrage opportunity" (arb) is when the two sides of a market — added together — pay out more than 100% of what you stake. The market is essentially mispriced.

Markets are usually built to give the book a small hold (3-5%). When two different books price the same event in opposite directions, the gap occasionally closes that hold and pushes through into negative territory for the book — which means positive for you.

You bet both sides, in the right proportions, and you walk with a small profit on both sides regardless of the outcome.

Where the gaps come from

One book is slow updating after a big news event (an injury, a starting-pitcher scratch)
Promo-boosted prices on one book temporarily push odds way out of line
Smaller regional books copy prices from larger ones imperfectly
Live betting odds that lag in-game movement

Sharp's Arb Finder scans dozens of books in real time and surfaces qualifying gaps. You don't have to spot these manually; the tool does. Your job is execution.

The math

Two books on the same NBA game:

Book A has the Lakers moneyline at +130 → decimal 2.30
Book B has the Celtics moneyline at -110 → decimal 1.909

The implied probabilities:

Lakers: 1 / 2.30 = 43.5%
Celtics: 1 / 1.909 = 52.4%

Add them: 95.9%. That's less than 100% — which means it's an arb.

The 4.1% gap is the covered profit pool. You stake on both sides in proportion to the prices.

Sizing both sides

To split a $200 total stake across both sides for a covered profit:

Lakers stake = $200 × (1.909 / (2.30 + 1.909)) = $200 × 0.4536 = $90.71 at Book A
Celtics stake = $200 × (2.30 / (2.30 + 1.909)) = $200 × 0.5464 = $109.29 at Book B

Round to whole dollars: $91 on the Lakers at A, $109 on the Celtics at B.

The payouts:

If Lakers win: $91 × 2.30 = $209.30 collected, $200 staked total → +$9.30 profit
If Celtics win: $109 × 1.909 = $208.08 collected, $200 staked total → +$8.08 profit

Either way you walk with about $8–$9 of profit on both sides on $200 staked — about 4% covered. That's the arb.

The seven mistakes that turn arbs into losses

Slow execution — one side hits, the other moves before you get there. Have both browser tabs queued and both stakes pre-calculated before you click anything.
Stake imbalance — guessing at stake sizes instead of using the formula. You can turn a covered profit into a one-sided risk in seconds.
Different markets — betting the moneyline on one book and the spread on another. They're not the same market. Always confirm market type matches.
Wrong rules — overtime rules, push rules, ejection rules differ between books. A "game" on Book A might not pay the same way as "game" on Book B for certain edge cases. Read the rules.
Canceled bets — if one side gets voided (player scratch, line removed), your "arb" becomes a single-sided bet at the other book. Watch the slip statuses.
Currency / vig changes mid-keystroke — odds move in real time. Confirm the price you got matches what you calculated against.
Bonus-bet conversions — promo and bonus money pays out differently than cash. Don't arb with bonus money without adjusting the math.

Limit risk — read this before you start

Sportsbooks limit or close the accounts of bettors who arb heavily, especially at recreational US books (DraftKings, FanDuel, BetMGM, etc.). Pinnacle and a few others welcome arbing. The major US books do not.

The defensive moves:

Mix arb bets with normal recreational-looking bets (parlays, big-name favorites)
Don't always max-stake to round numbers like $500 — looks robotic
Spread your arbing across many books, not the same two over and over
Take some of the smaller +EV "value" bets too, not just arbs

Avoiding the limit — stake sizing + book rotation for arbing covers the longer game of staying off the limit list.