Odds & Probability

American odds use a baseline of 100. A positive number is the profit on a $100 stake (+250 wins $250). A negative number is the stake needed to win $100 (-150 means risking $150 to win $100).

Closing line value measures whether the price you took was better than the final price before the event started. Consistently positive CLV predicts long-term profitability far more reliably than your win rate does.

Decimal odds show the total return per unit staked, including the stake itself. Odds of 3.50 return £3.50 for every £1 bet. £2.50 profit plus your £1 back.

Devigging is removing the bookmaker's margin from a set of odds to recover the market's honest probability estimate. It converts a price that implies 52.4% into the roughly 50% the book actually believes.

Even money is a price where you win exactly what you stake. Written as 1/1, 2.00 or +100, it implies a 50% chance before any bookmaker margin is considered.

The favourite is the selection with the shortest odds in a market, meaning the bookmaker rates it most likely to win. Favourites win roughly a third of horse races and are generally better value than their reputation suggests.

Fractional odds show profit relative to stake. 5/1 means five units of profit for every one staked; 5/2 means five profit for every two staked. Your stake is returned separately on top.

Implied probability is the chance of an outcome suggested by its odds. Divide 1 by decimal odds: a price of 4.00 implies 25%. It always overstates the real probability, because the bookmaker's margin is built in.

The line is the number a sportsbook sets for a market. The points handicap, the total, or the odds themselves. Betting the line means accepting that number as the terms of your bet.

Line movement is the change in odds or handicap between a market opening and closing. It reflects incoming money and new information, and the direction of movement is often more informative than the price itself.

A long shot is a selection priced at very long odds, reflecting a low estimated chance of winning. Long shots are systematically overbet, which makes them worse value than their prices already suggest.

Odds conversion is translating between decimal, fractional and American formats, which all describe the same price differently. 2.50, 6/4 and +150 are identical odds, only the notation changes.

An odds-on selection is priced below even money, meaning you stake more than you stand to win. A 1/2 shot requires £20 to win £10, and implies a probability above 50%.

The opening line is the first price a sportsbook posts on a market. It is the least informed number the book will ever offer, which makes it both the best opportunity and the riskiest moment to bet.

Price is another word for odds. Taking a price means accepting the odds showing at the moment you bet, which then fixes your payout regardless of how the market moves afterwards.

Public money is the aggregate of recreational betting, characterised by a bias toward favourites, overs and popular teams. Books tolerate large imbalances of it because it is, on average, unprofitable.

Sharp money is betting volume from people the sportsbook considers informed and consistently profitable. Books move lines quickly in response to it, even when the amounts are small.

A steam move is a sudden, large and coordinated shift in a betting line across multiple sportsbooks at once, usually caused by a syndicate placing substantial bets simultaneously.

True odds are the actual mathematical probability of an outcome, as opposed to the odds a bookmaker offers. The gap between the two is the house edge, and in casino games it is exactly calculable.

The underdog is the selection the market rates less likely to win, shown at longer odds or with a plus sign in American formats. Underdogs receiving points on the spread only need to lose narrowly to cash.