True odds are what a selection would be priced at with no bookmaker margin in it: the price at which a bet neither gains nor loses on average. True odds betting is the habit of working that number out first and treating the bookmaker's quote as an offer to be measured against it, rather than as the going rate.
The part most definitions skip is where the number comes from. The real chance of a match is never observed, because the match happens once, so a true price is the output of a method and it carries the doubt of whatever market it was built from. How big that doubt gets is the useful question, and it is what the rest of this entry measures.
The offered price and the true price
A bookmaker's price is built to be sold, so it carries a margin. The true price is the same selection with that margin taken out, which is why the two numbers answer different questions.
| What it answers | Where it comes from | |
|---|---|---|
| Offered price | What will this bookmaker pay me | The bookmaker |
| True price | What is this bet worth | Your estimate, from a market |
American betting writing calls the same number no-vig odds, and the rest of this library calls it the fair price. Three names, one number.
How a true price is estimated
The usual method is to de-vig the market: turn every price into an implied chance, see how far the total sits above 100%, then scale the chances back until they add to 100%. Removing bookmaker margin sets out the methods and when each one suits, and the fair odds calculator runs them on your own prices.
Example: Illustrative prices on a two-way market, not a real event: one side $1.74, the other $2.22.
| Side | Offered | Implied | True price |
|---|---|---|---|
| A | $1.74 | 57.47% | $1.78 |
| B | $2.22 | 45.05% | $2.28 |
The two implied chances add to 102.52%, an overround of 2.52 percentage points. Scaling both down by that factor is the same sum as multiplying each price by 1.0252: 1.74 x 1.0252 = $1.78 and 2.22 x 1.0252 = $2.28. The scaled chances, 56.06% and 43.94%, add to 100%.
The comparison is then one line: edge = offered price / true price - 1, and a bet is only worth taking where that number is positive. Say a second bookmaker offers $1.82 on side A: 1.82 / 1.7838 - 1 = 0.0203, an edge of 2.03% against the unrounded true price. Against the rounded $1.78 it reads 2.25%, so the working stays unrounded until the last step.
Risk: Betting involves risk. Bookmakers can restrict or close accounts and void bets, prices move, and a positive expected value bet can still lose. There is no guarantee of profit. See responsible gambling for limits and support.
The estimate is only as good as the market behind it
De-vigging answers "what does this market imply", not "what is true", so changing the market changes the answer.
Example: Illustrative. A second bookmaker quotes the same two sides at $1.69 and $2.33.
1 / 1.69 = 59.17% and 1 / 2.33 = 42.92%, a book of 102.09%, so the true prices become 1.69 x 1.0209 = $1.73 and 2.33 x 1.0209 = $2.38.
Side A now has a true price of $1.78 from one market and $1.73 from the other. Those two answers sit 1.7838 / 1.7253 - 1 = 3.39% apart, which is wider than the 2.03% edge they were being used to measure, so on these illustrative numbers which market you de-vigged decided the answer. A thin, stale or one-sided market widens that gap, and a true price worked out an hour before the start describes an hour-old market. The scaling adds doubt of its own, which is what the power method and the Shin method set out to narrow.
That makes the usable test comparative rather than absolute: an edge smaller than the spread between your own estimates is not an edge.
Finding prices above a true price on B337
B337's +EV screener runs this comparison across sports markets, listing bookmaker prices above the fair price and ranking them by edge. Its fair price comes from taking the margin out of prices across the market, including exchanges and a global market reference, combined into one estimate per selection, and the de-vig is adjustable, with every edge worked out again to match. On racing, the Terminal's EV overlays compare each bookmaker's price with the Betfair exchange market instead. Both are estimates, not known chances. Screener rows come with Terminal Pro, Full Automation or the Screeners plan; a free account shows the live count above fair with the rows locked.
Risk: Betting involves risk. A fair price is an estimate, and a positive expected value bet can still lose. There is no guarantee of profit. See responsible gambling for limits and support. For free and confidential support call 1800 858 858 or visit gamblinghelponline.org.au.