Betting glossary: EV, CLV, arbitrage and more

Arbitrage (surebet)

Backing every outcome of a market at different bookmakers when the best prices' implied probabilities total less than 100%, so the return at those prices is the same whatever the result. Voided bets, price changes and stake limits can still break it.

Σ(1 / best odds) < 1

Bankroll

Money set aside only for betting, kept separate from everyday funds. Stakes, units and Kelly fractions are all measured against it.

Bookmaker margin (overround, vig)

The bookmaker's built-in edge: the sum of the implied probabilities of all outcomes minus 100%. A 1X2 market that adds up to 105% carries a 5% margin. The lower the margin, the better the prices.

margin = Σ(1 / odds) − 1

Closing line

The last odds offered before the event starts. At a sharp bookmaker it is the most accurate public estimate of the probability, because it reflects all money and news up to kickoff.

Closing line value (CLV)

How much better your odds were than the closing line. Taking 2.20 on a price that closes at 2.00 is +10% CLV. Consistently positive CLV is the most reliable early sign of a long-term edge.

CLV = your odds / closing odds − 1

De-vig (no-vig odds)

Removing the margin from a market to estimate the true probabilities. The simplest method divides each implied probability by the market total so they sum to 100%; other methods assign more of the margin to longshots.

p = (1 / odds) ÷ Σ(1 / odds)

Decimal odds

The total return per unit staked, stake included. A €10 bet at 2.45 returns €24.50, of which €14.50 is profit. kefas shows all odds as decimals with two places.

return = stake × odds

Expected value (EV)

The average profit or loss per unit staked if you could place the same bet many times. Positive EV means the odds are higher than the fair odds; kefas shows it as a percentage of the stake.

EV = p × odds − 1

Fair odds

The odds with the bookmaker's margin removed, equal to 1 divided by the true probability. kefas derives them from the sharp reference price after de-vigging it. Any price above the fair odds is a value bet.

fair odds = 1 / p

Hedge (lock)

A bet against a position you already hold, to cut risk or lock in a result. Hedging an open bet whose price has shortened can secure a profit on every outcome at the cost of part of the upside.

Implied probability

The chance a price implies: 1 divided by the decimal odds, so 2.50 implies 40%. Across all outcomes of one market these add up to more than 100%; the excess is the margin.

p = 1 / odds

Kelly criterion

A staking formula that sizes each bet as a share of your bankroll in proportion to your edge. Full Kelly swings hard, so most bettors stake a fraction of it; kefas shows ⅓ Kelly.

f = (p × odds − 1) / (odds − 1)

Line movement

A change in a market's odds after it opens, driven by money, news such as injuries or line-ups, or one bookmaker copying another. Soft books often move later than sharp ones, which briefly leaves value on the table.

Low hold

A market where the best available prices across bookmakers add up to only slightly more than 100%. Such markets cost little to bet into, which makes them useful for clearing bonus wagering requirements.

Middle

Two bets on opposite sides of a market at different lines, for example over 2.5 goals at one book and under 3.5 at another. If the result lands between the lines both bets win; otherwise one wins and the loss is usually small.

Sharp bookmaker (Pinnacle)

A bookmaker that accepts large bets from professionals, runs low margins and corrects its prices quickly. Its odds are the best public estimate of true probability; Pinnacle is the best-known example and kefas's reference.

Soft bookmaker

A bookmaker aimed at recreational bettors, with higher margins, slower price updates and stake limits for winning customers. This is where most value bets appear.

Steam move

A sudden, sharp move of the same line across many bookmakers at once, usually set off by large professional bets at a sharp book. Books that have not moved yet briefly offer outdated prices.

Unit

A standard stake size, usually 1–2% of the bankroll. Recording results in units rather than euros makes them comparable across bettors and bankroll sizes.

Value bet

A bet whose odds are higher than the fair odds, so its expected value is positive. A single value bet can still lose; the edge only shows over many bets.