Arbitrage and its variations
- Arb (arbitrage)
- Opposite bets across sportsbooks whose prices imply less than 100% combined probability. Balanced stakes give a calculated positive return. See What is betting arbitrage.
- Surebet
- Another name for an arb. The calculation is conditional on acceptance and settlement; execution still carries risk.
- Midarb (middle)
- Over a lower line and under a higher line. Both win inside the window; outside usually incurs a small loss. See Betting middles.
- Leg
- One bet in an arb or middle. A two-way arb has two legs; 1X2 has three. An open leg is exposure left when the planned opposite bets aren't all accepted.
Odds and margin
- Decimal odds
- Total payout per unit staked. $100 at 2.10 pays $210. Implied probability is 1 / odds.
- American odds
- Positive odds show profit per $100 staked: +150 equals 2.50. Negative odds show the stake needed for $100 profit: −200 equals 1.50. Use the odds converter.
- Margin (overround)
- Combined implied probability above 100% across one market's outcomes. See Sportsbook margin and fair odds.
- Odds fair
- Odds after removing margin under a chosen method. Use the margin calculator. They aren't the true event probabilities.
Markets and lines
- Handicap
- A score adjustment, such as −4.5 points. The adjusted side must win by at least five points to cover that line.
- Total
- The total goals, points, games or runs in an event or period. Bet over or under its line.
- Over/under
- At 2.5 goals, over wins from three and under up to two. Half lines can't push; whole lines may refund the stake at the exact total under applicable rules.
- Prematch i live
- Prematch means before the event; live means during it. In-play prices move quickly and acceptance may be delayed.
- Line
- The boundary for a total or handicap, such as 21.5 games or −4.5 points. Different lines create middle windows.
Settlement and accounts
- Void (zwrot)
- A voided bet usually returns the stake at settlement odds of 1.00. The reasons and conditions depend on sportsbook rules.
- Krecz
- A tennis player stops before finishing. Settlement varies; the board flags known mismatches.
- Limit
- A sportsbook restriction, such as reduced stakes, manual acceptance or unavailable markets. See Account limits.
- Bankroll
- Money allocated to betting across your accounts. Use only an amount you can afford to lose.
- Stake
- The amount placed on one leg. Arbitrage stakes are balanced using the implied probabilities.
Measuring results
- Expected value (EV)
- The probability-weighted average return: win probability × net win minus loss probability × stake. Positive EV is an expectation, not a guaranteed realised result.
- ROI
- Return on investment: profit divided by total stakes. ROI of 2% gives $2 per $100 staked across the pair.
- Kelly criterion
- Kelly sizes bets with an estimated edge: f = (b·p − q) / b, where b = odds − 1 and q = 1 − p. Fractional Kelly reduces stake size. See the Kelly calculator.
- Closing odds
- The last available price before the event starts. It reflects information and betting activity available to the market at that time.
- CLV (closing line value)
- How your taken odds compare with closing odds. Consistently beating the close can indicate an edge, but isn't proof of guaranteed future profit.
Put it into practice