Betting odds types explained

Australian prices are quoted in decimal odds. The number is the total return on $1.00, stake included: $10.00 at $4.00 returns $40.00, which is $30.00 of profit plus the $10.00 back. Overseas you will still meet fractional odds, where the number is the profit alone, and American moneylines, which quote how much you must stake to win 100 or how much 100 wins.

The sum that matters

Divide 1 by a decimal price and you have the chance it implies. $4.00 is 25.0%, $2.00 is 50.0%, $1.50 is 66.7%. Most of what follows is built on that: a price is value only when it implies a smaller chance than a fair estimate of the true one, which is what +EV betting measures, and a +EV bet can still lose.

Adding a card up: the overround

Do that sum for every outcome in one market and add the results. A fair market totals 100%. A bookmaker's card totals more, and the excess is the overround, built into the prices before you see them. It is close to, but not the same as, what a bookmaker keeps: a balanced book at 105% keeps 1 - 1 / 1.05 = about 4.8% of the money staked. An exchange, where punters bet against each other and the exchange charges commission on winnings instead, totals much closer to 100%, which is why exchange prices are used as the fair reference.

A fixed-odds bet settles at the price the bookmaker accepted, whatever happens to the market afterwards, with the one racing exception below. It is the default for sport and is offered on racing beside the tote, and it is the kind you can compare between bookmakers in advance, because the price a bookmaker accepts is the price the bet settles at.

The price you see is an offer, not a promise: a bookmaker can change it, and a bet counts at the price it accepts, which can be lower than the one you clicked. And if a runner is scratched, bets on it are refunded (except futures bets struck before final acceptances, which can be all in), while a winning fixed-odds bet on another runner, placed before the scratching, can be paid less a deduction in cents in the dollar that the stewards declare. The bookmaker's terms say how the deduction is applied, so a short-priced withdrawal changes what the rest of the field pays.

On the tote, every bet of one type on a race goes into one pool: win bets into the win pool, place bets into the place pool, and so on for each bet type. When betting closes the operator takes its commission, and what remains is shared among the winning tickets. So the dividend depends on how much went into the pool, the operator's commission and how much of it backed the winner, and it is declared only after the result. The figure on screen before the jump is an approximate, not a price.

A worked sketch, with made-up numbers: say a win pool holds $8,500 once the operator's commission is out, and $1,200 of the bets in it were on the winner. The dividend is $8,500 / $1,200 = $7.08 back for every $1.00 on it, stake included, before rounding. Dividends are rounded down to a multiple of 5c under the Northern Territory tote rules, so this one would be declared at $7.05. Take a figure like that as arithmetic, not a real pool: the commission is set by the operator for each pool.

A starting price is a price struck at the jump rather than one you took earlier. For a bookmaker bet, the bookmaker's terms say which price settles it. In NSW, Racing NSW says that since May 2017 the price fluctuations, the starting price and the top fluc for the NSW meetings it covers come from the NSW Official Price service, calculated from the larger wagering operators' fixed odds. On the Betfair exchange the starting price has its own name, Betfair Starting Price or BSP. It is formed at the jump from the money waiting on each side, and some racing bets can be settled at it instead of at the price showing when the bet was placed.

Why it matters beyond settling bets: a starting price is the nearest thing racing has to a closing line, so it is the fairest after-the-fact check on a price you took. If you regularly take prices above the eventual starting price, your timing is adding something; if you take prices below it, it is not, whatever the results happened to do. That is also the thinking behind the closing lines the Terminal records: the last prices before the jump.

• Totals, or over/under. The bookmaker names a number and you back the total to be above or below it. Totals move by whole and half points, and different bookmakers hold different numbers on the same game.
• Handicaps, lines and the start. One side is given a head start in points and the bet is settled on the adjusted result.
• Why the half point. A whole-number line can land exactly on the number, and the bookmaker's rules then decide the bet, for example by voiding it and returning the stake. A half-line cannot land on the number, so every bet has a result.
• Why two bookmakers' lines differ. Each sets its own, and moves it at its own pace. That disagreement is what middle betting and arbitrage betting are built on.

Sorting the kinds out has one practical payoff: knowing which prices can usefully be put side by side before an event. Fixed odds can, because the accepted price is the price the bet settles at. Exchange back and lay prices can, because they are offers someone is making now. A tote dividend cannot, because it does not exist yet, and a tote-derived bookmaker product cannot either, since what it will settle at depends on dividends nobody has declared.

That is the shape of the B337 Terminal. It is a live odds board carrying fixed racing and sports prices from 40+ bookmakers side by side, with Betfair back and lay beside them, price history so you can tell a firming runner from a drifting one, closing lines, and EV overlays that compare each bookmaker price with an estimated fair price (on racing, Betfair's own market). Each bookmaker column is a fixed-odds offer, a price that was on offer when it was read: prices are read on a repeating cycle, not tick by tick, so a price on screen can trail the bookmaker's own. Confirm it in your bookmaker account before you bet.

The Terminal is an odds board, not a bookmaker: B337 takes no bets, sets no prices and holds none of your money, so your stakes and winnings stay in your own accounts. B337 is not affiliated with Betfair. For how it uses those comparisons on racing, see the horse racing betting bot; for what the board shows and where the prices come from, odds comparison.