💡 The value bet is the core concept behind any methodical approach. It is the only idea that allows, in theory, a positive expected value over a very large number of bets, with no certainty of results whatsoever. Here is the calculation and its pitfalls.
Defining the Value Bet
A value bet exists when the estimated probability of an event is higher than the implied probability of the odds offered by the bookmaker.
In other words: if your estimate is correct, the odds pay more than the real risk. Everything rests on that “if”: an estimate can be wrong.
Simple formula: Value = (Estimated probability × Odds) − 1
If the result is positive → value bet (opportunity) | If negative → no value
A Concrete Example
Situation: Arsenal are playing an average side. Suppose a model estimates that Arsenal have a 70% chance of winning, and a bookmaker offers odds of 1.60 on an Arsenal win.
Calculation: (0.70 × 1.60) − 1 = +12% value
This means the odds of 1.60 are 12% above the fair odds for a 70% chance (1 ÷ 0.70 = 1.43), provided the 70% estimate is correct. Over a few dozen bets, the actual result may be very different.
What IASHARK Actually Calculates
The IASHARK model estimates each team's attacking and defensive strength, at home and away, then the probability of each score and each market (details on the Methodology page):
- Included in the calculation — goals scored and conceded, chance quality when the data is sufficient, the previous season early in the season, a correction for overconfidence on some markets
- Not included in the calculation — weather, fatigue, what is at stake in the match and absences, shown as context only
- Odds — those offered by bookmakers, once their margin is removed: the chance shown takes into account both the model and the odds
For each match, the option highlighted is chosen by a fixed rule among the markets actually priced by bookmakers, favouring the most likely outcomes, not the one with the largest gap. The gap is shown separately. The “Favourable gap” label only appears from a gap of 3 points.
The Different Types of Value Bets
Straight Value Bet
The most direct bet: win, draw or loss. It is the most followed market, so the one where the odds already include the most information.
BTTS Value Bet (Both Teams To Score)
Do both teams score? The probability comes from the same score grid as the match result, and a gap is read in the same way.
Over/Under Value Bet
Total goals depends directly on the attacking and defensive strength of both teams. The question is whether the odds already account for it.
Out of Scope: Long-Term Bets
Winner of a league or a competition: IASHARK does not analyse these bets. The model works match by match, on football only.
Stakes — What IASHARK Does Not Say
Once a gap has been spotted, there remains the question of the amount. IASHARK does not suggest any stake. Formulas that size the stake according to the gap assume an exact probability: if it is overestimated, they make you stake too much. The decision to bet, and how much, remains yours.
Mistakes to Avoid
Mistake #2: Staking too much. Even when the gap looks wide, a big stake exposes you to ruin: losing streaks happen even with correct estimates.
Mistake #3: Only picking heavy favourites. Very short odds pay little, and a single failure wipes out several successes. A high probability is never a certainty.
Value Bet vs Other Strategies
No strategy removes the risk. Doubling the stake after a loss speeds up losses instead of wiping them out. Arbitrage runs into moving odds and account restrictions. Betting at random amounts to paying the operator's margin. Value betting is only a way of reasoning: it is never worth more than the initial estimate.
Frequently Asked Questions
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