How we profit from multi promos
Promo mode in Multi Smasher evaluates two types of promotion. Value Builder also supports regular value multis without promotion terms:
The Multi Smasher works by calculating the expected return of each outcome of your multi bet, taking into account both the odds of each leg and the promotion being applied.
Then, we calculate the overall expected value (EV) of the multi bet by combining the expected returns of all possible outcomes, weighted by their probabilities.
Multi Smasher supports regular multis and same-game multi (SGM) leg guidance. Regular multis have a combined calculation. SGM shows individual leg estimates; it does not estimate the combined SGM price.
Hedged Promo uses exchange lay odds to calculate hedge stakes and outcome returns. It is available for regular multis.
Unhedged Promo, Value Builder, and SGM use the shared EV sources: Derived, Line, Implied, and Sharp. Derived removes bookmaker margin at the exact proposition. Line uses nearby qualifying consensus lines. Implied uses weighted market-average prices for fallback candidates. Sharp uses selected bookmakers' raw reference prices.
Each source estimates the fair price of an individual leg. For a regular multi, combining leg probabilities assumes independence. For an SGM, correlations mean that this product does not establish the combined fair probability.
See the source guide for the pricing methods and the Multi filters guide for their controls.
The number of outcomes we need to consider grows exponentially depending on the number of legs in the multi, where
Consider a 3 leg multi - there are 2^3 = 8 possible outcomes:
WWW
WWL
WLW
WLL
LWW
LWL
LLW
LLL
Where W = leg wins, L = leg loses.
Depending on the type of promotion and whether or not you're laying the multi, each outcome will have a different expected return.
Let us consider just the first outcome (WWW) for both a profit boost promotion, and a bonus back promotion.
Let's imagine a bookmaker is offering a 20% profit boost on winning multis. We know that our multi has total odds of 7.0, and we've staked $10 on it. We also know the fair odds of winning the multi are 1 in 8 (12.5% probability, or odds of 8.0).
If the multi wins, the expected return is calculated as follows:
Profit = (Total Odds * Stake) - Stake = (7.0 * $10) - $10 = $60
Boosted Profit = Profit * (1 + Profit Boost %) = $60 * 1.20 = $72
The net profit is $72 if the multi wins and -$10 if it loses.
Expected profit = ($72 × 12.5%) + (-$10 × 87.5%) = $9.00 - $8.75 = $0.25.
That is a 2.5% expected return on the $10 stake, using the assumed 12.5% fair win probability. Do not include the returned stake in winning profit while also counting the lost stake in losing profit.
There are 3 scenarios where a bonus would be paid out in a 3 leg multi - if the first, second or third leg loses, but the others win. Each of these outcomes has a different probability of occuring, as does the WWW outcome.
To calculate the EV of this multi bet, it would follow that:
The sum of all these EVs would give you the overall EV of the multi bet.
When you're laying multi bets, you're aiming to reduce variance. This means that each outcome now has the return of x lay bets to consider, where x is the number of legs in the multi.
Consider the LLL outcome in a 3 leg multi. If all legs lose, the multi bet loses, but each of the 3 lay bets wins. Therefore, instead of simply losing your stake, the LLL outcome is likely to become that one that returns the greatest profit.
Conversely, any outcome with just a single losing leg will see the amount lost increase. The overall expected value of the multi bet will therefore be lower when laying, but the variance will also be reduced.