To value a betting promotion, work out its expected value: for each way the bet can finish, multiply what you would receive by the chance of that finish, add the results and subtract your stake. Exchange prices supply the chances, because 1 / price turns a price into an estimated probability, so one sum covers a boost, a refund, a bonus bet or a qualifying spend.
A positive answer means the offer more than covers the bookmaker's margin on average, over many bets like it. It says nothing about the next bet, and the terms decide how much of the value you can collect: the cap, the minimum odds, the qualifying bets and whether the payout is cash or a bonus bet.
Promo expected value: one formula for every offer
With one bracket for each way the bet can finish:
expected value = (chance of outcome 1 x what you receive in outcome 1) + (chance of outcome 2 x what you receive in outcome 2) + ... - stake
Three inputs go into it:
- The chances: 1 / fair price for each outcome, where a common estimate of the fair price sits between the exchange back and lay prices. Fair odds covers other ways to build one, and every one is an estimate.
- What you receive: a winning cash bet returns stake x price, stake included, and a cash refund counts in full. A bonus bet counts only at the share of its face value you expect to keep.
- The stake: only your own money counts, so a bet placed with a bonus bet has no cash stake.
It is the same test value betting applies to an ordinary bet. A promotion adds outcomes that pay something extra, and each shape adds its own:
| Promotion | Outcomes to price | Where the extra value comes from |
|---|---|---|
| Odds boost | Win, lose | The higher price on a win, up to the cap |
| Money back if second or third | Win, refund placing, unplaced | The refund, in cash or as a bonus bet |
| Early payout | Win, reach the trigger lead then lose, neither | A payout as a winner once the lead triggers |
| Refund if a team loses narrowly | Win, lose inside the margin, lose by more | The refund, priced from two exchange markets |
| Bet and get | The qualifying bet's outcomes, then the bonus bet | The bonus bet, less what the qualifying bet costs |
Money back racing promos works the racing refund from exchange win and place prices, early payout promotions the lead trigger, and odds boosts explained the boost shapes, while betting promotions in Australia maps every type.
Worked example: an odds boost with a maximum stake
Example: Illustrative prices, not a current offer or a real game. Team A is $2.85 to win with Bookmaker A, which boosts it to $3.30 on stakes up to $40, with any stake above $40 settled at $2.85. On the exchange, Team A is $3.10 to back and $3.15 to lay.
Fair price = (3.10 + 3.15) / 2 = 3.125, so the win chance = 1 / 3.125 = 32%.
| Bet | Working | Expected value |
|---|---|---|
| $40 at the boosted $3.30 | 32% x $40 x 3.30 - $40 | +$2.24 |
| $40 at the normal $2.85 | 32% x $40 x 2.85 - $40 | -$3.52 |
| $120: $40 at $3.30 and $80 at $2.85 | +$2.24 + (32% x $80 x 2.85 - $80) | -$4.80 |
- The boost adds 32% x $40 x (3.30 - 2.85) = $5.76, turning -$3.52 into +$2.24. That is the edge, 3.30 / 3.125 - 1 = 5.6%, times the $40 stake.
- Every dollar above the cap is a plain bet at $2.85, which loses 1 - 2.85 / 3.125 = 8.8 cents on average. $2.24 / $0.088 = about $25.45 of overflow wipes out the $2.24, so a total stake above about $40 + $25.45 = $65.45 makes the whole bet negative.
- The boosted bet still loses 68% of the time, and then it returns nothing.
Where the terms refuse stakes above the cap instead, the $120 row does not apply. The expected value calculator runs this sum on your own prices.
Risk: Betting involves risk. A boost that beats the fair price is positive on average, and a +EV bet can still lose, and often does. See responsible gambling for limits and support.
Bonus bet refunds count as bonus bets, not cash
A bonus bet refund is worth less than the same amount of cash, because a winning bonus bet usually pays only its winnings. Used at a bookmaker price b on a selection the exchange prices at a fair f, a bonus bet keeps (b - 1) / f of its face value on average: at $3.80 against a fair $4.00, that is (3.80 - 1) / 4.00 = 70%.
Example: Illustrative prices, not a current offer or a real game. You bet $80 at $2.35 on Team B in a basketball game, which cannot be drawn, with an offer to refund your stake as a bonus bet if Team B loses by 5 points or fewer. The exchange has Team B at a fair $2.50 to win and a fair $1.60 to cover a line of +5.5 points.
Team B covers +5.5 if it wins or loses by 1 to 5, so the refund chance = 1 / 1.60 - 1 / 2.50 = 62.5% - 40% = 22.5%.
| Outcome | Chance | What you receive | Chance x what you receive |
|---|---|---|---|
| Team B wins | 40% | $80 x 2.35 = $188 in cash | $75.20 |
| Loses by 1 to 5 points | 22.5% | An $80 bonus bet, worth $80 x 70% = $56 | $12.60 |
| Loses by 6 or more | 37.5% | Nothing | $0.00 |
| Total | 100% | $87.80 |
Expected value = $87.80 - $80 = +$7.80. Counted as $80 of cash, the refund would be worth 22.5% x $80 = $18.00 instead of $12.60, overstating the offer by $5.40.
If you would hedge the bonus bet rather than bet it outright, value it at what the hedge keeps. With an exchange lay at $4.10 and an illustrative commission rate of 5%, the bonus bet converter formula keeps $80 x (3.80 - 1) / (4.10 - 0.05) x (1 - 0.05) = $52.54 either way, or $52.54 / $80 = 65.7%, if the lay is matched in full. On that basis the refund adds 22.5% x $52.54 = $11.82, and the bet is worth -$4.80 + $11.82 = +$7.02.
The national framework makes a bonus bet's winnings withdrawable with no turnover attached, so once a bonus bet wins, what it pays counts as cash.
Risk: Betting involves risk. The refund only follows a losing bet, a bonus bet that loses pays nothing, a lay can go unmatched and the two bets can settle differently, and a bookmaker can limit stakes, restrict promotions, void bets or close an account. See responsible gambling for limits and support.
Qualifying spend, caps and minimum odds in the sum
Terms change the sum in three places: a cap limits the stake covered, as the boost example shows, a minimum price limits which bets count, and a qualifying bet is a cost in its own right.
Example: Illustrative offer and prices, not a current offer. Bet $100 at $2.00 or longer on a race and receive a $25 bonus bet. You choose Runner 7 at $5.70, which the exchange prices at a fair $6.00, and you would use the bonus bet at the 70% share worked out above.
- Expected value of the qualifying bet: $100 x (5.70 / 6.00 - 1) = -$5.00, a cost of $5.00
- Value of the bonus bet: $25 x 70% = $17.50
- Value of the offer: $17.50 - $5.00 = +$12.50
The minimum price costs nothing by itself. What costs is how far the price you take sits below fair. A qualifying bet at $2.10 against a fair $2.30 has an expected value of $100 x (2.10 / 2.30 - 1) = -$8.70, a cost of $8.70, so the same offer is worth $17.50 - $8.70 = +$8.80. If the qualifying spend is split across several bets, add up each bet's cost the same way. Where an offer needs a set amount of betting, betting turnover requirements shows what that turnover costs.
Risk: Betting involves risk. The qualifying bet can lose its whole $100, and these figures are averages over many offers, not the result of this one. See responsible gambling for limits and support.
When the bookmaker decides a bet does not qualify
Every figure above assumes the bet qualifies, and under its terms the bookmaker decides whether it does. A bet that misses the offer earns nothing extra: in the refund example, the bet falls back to its plain value, $80 x (2.35 / 2.50 - 1) = -$4.80, and loses the $12.60 the refund was worth. Common reasons a bet misses out:
- it was placed before you opted in, where the offer needs an opt-in
- it was the wrong bet type or market, such as an each way bet on a win-only offer
- its price was under the minimum, or its stake over the cap
- it was placed with another bonus bet
- the result fell into a case the terms treat differently, such as a dead heat, a protest or a late scratching
Restrictions on promotions sit with the bookmaker too: the NT Wagering Commission, which licenses many online bookmakers, takes complaints about how a wager was handled but cannot look into restrictions an operator puts on an account, including on its promotions. Where the terms are unclear, value the offer at zero until the bookmaker confirms in writing, and keep screenshots of the offer, its terms and your bet.
Is a betting promotion worth it? A decision rule
Take a promotion when all four of these hold:
- Its expected value is positive after the qualifying bets, at a stake inside the cap.
- The bet is one you would consider without the offer, at a price close to fair.
- The stake comes from money you had already set aside for betting.
- You can use any bonus bet before it expires without adding cash bets to do so.
Skip it when it needs extra bets you would not otherwise place, pushes you to a worse price, or comes with terms you cannot pin down. Promotions are inducements, built to get you betting more often, and if offers are setting your betting instead of your own plan, how to stop betting promotions covers opting out.
Risk: Betting involves risk. Passing all four tests makes a promotion positive on average only: the bet can still lose, and a bonus bet that loses pays nothing. See responsible gambling for limits and support.
Mistakes that inflate a promotion's value
| Mistake | What it costs in these examples |
|---|---|
| Measuring a boost against the bookmaker's normal price, not the fair price | The $40 boost looks worth 40 x (3.30 / 2.85 - 1) = $6.32, overstating it by $6.32 - $2.24 = $4.08 |
| Staking past the cap | +$2.24 becomes -$4.80 at a $120 stake |
| Counting a bonus bet refund as cash | The refund offer is overstated by $5.40 |
| Leaving out the qualifying bet | The bet-and-get offer shows as +$17.50 instead of +$12.50 |
| Ignoring commission when you plan to hedge | An $80 bonus bet looks worth $80 x (3.80 - 1) / 4.10 = $54.63 instead of $52.54 |
| Betting before you opt in | +$7.80 becomes -$4.80 |
Checking fair prices on B337's Terminal
B337's Terminal shows many of the inputs for these sums side by side: prices from 40+ bookmakers across racing and sports, Betfair back and lay beside them, and EV overlays. The overlays set each price against an estimated fair price: Betfair's market for racing, and a global market reference with the margin removed for sports. Betfair prices and EV overlays start at Terminal View; a free account opens a limited view of the Terminal with live odds. The free calculators on the odds comparison page include a racing promo calculator for a promotion already in your account.
The Terminal reads prices on a repeating cycle, so treat a price on screen as a guide and confirm it in your bookmaker account before betting. Bookmaker names are trade marks of their owners. B337 is not affiliated with them.
For free and confidential support call 1800 858 858 or visit gamblinghelponline.org.au.
Risk: Betting involves risk. EV overlays are estimates rather than forecasts, and there is no guarantee of profit from any promotion. See responsible gambling for limits and support.