BetBotHomeProfessional bet sizing for long-term bankroll growth. Calculate the mathematically optimal stake for any bet based on your edge and the odds.
Enter the decimal odds and your estimated win probability to calculate optimal stake sizes.
The Kelly Criterion is a mathematical formula developed by John L. Kelly Jr. at Bell Labs in 1956. It calculates the optimal percentage of your bankroll to stake on a bet where you have an edge. The goal is to maximize the long-term growth rate of your bankroll while minimizing the risk of ruin.
In football betting, this means sizing your bets based on how much value you have identified. A strong edge at high odds warrants a larger stake. A slim edge at short odds warrants a smaller one. Instead of flat-staking every bet at 2% or guessing how much feels right, Kelly gives you a precise, mathematically grounded answer.
The formula is straightforward: Kelly % = ((odds - 1) x probability - (1 - probability)) / (odds - 1). If the result is positive, you have a value bet. If it is negative, the odds do not offer enough value and you should skip the bet entirely.
Full Kelly maximizes theoretical bankroll growth but assumes your probability estimates are perfectly accurate. In real-world football betting, they never are. That is why most professionals use fractional Kelly, staking a fraction of the full amount to account for estimation error.
You are looking at a Premier League match where the bookmaker offers 2.10 for Over 2.5 Goals. After analysing recent form, head-to-head records, and team profiles, you estimate the true probability of this outcome at 55%.
Odds: 2.10 | Your estimated probability: 55% (0.55)
Kelly % = ((2.10 - 1) x 0.55 - (1 - 0.55)) / (2.10 - 1)
Kelly % = (1.10 x 0.55 - 0.45) / 1.10 = (0.605 - 0.45) / 1.10 = 0.1409 = 14.1%
With a $1,000 bankroll, Full Kelly says stake $141. That is aggressive. Half Kelly would be $70, and Quarter Kelly would be $35. Most professionals would go with the Half Kelly stake here, balancing growth with risk management.
Kelly never recommends staking your entire bankroll. The formula inherently limits bet size relative to your edge, protecting you from catastrophic losses.
No other staking strategy grows your bankroll faster in the long run. Kelly is mathematically proven to maximize the geometric growth rate of wealth.
Fractional Kelly lets you dial variance up or down. Half Kelly gives smoother returns. Quarter Kelly is conservative enough for parlays and accumulators.
Kelly forces discipline. It prevents you from overbetting when confident and underbetting when uncertain. Over hundreds of bets, this edge compounds significantly.
The Kelly Criterion is a mathematical formula that calculates the optimal percentage of your bankroll to stake on a bet. It balances risk and reward by considering the odds offered and your estimated probability of winning. The result tells you exactly how much to bet to maximize long-term bankroll growth.
Full Kelly maximizes theoretical growth but assumes your probability estimates are perfectly accurate. In practice, estimates are always slightly off. Half Kelly stakes half the recommended amount, which reduces variance by roughly 75% while only sacrificing about 25% of long-term growth. Most professional bettors use half or quarter Kelly.
A negative Kelly percentage means there is no value in the bet. The odds offered do not compensate for the risk based on your estimated probability. You should skip any bet where the Kelly formula returns a negative number, as it indicates a negative expected value.
You can apply Kelly staking to accumulators by estimating the combined probability of all legs winning and using the combined decimal odds. However, because accumulators multiply uncertainty across multiple events, most bettors use quarter Kelly or less for parlays to account for the compounded estimation error.
BetBot analyses odds and form across 50+ leagues daily — pair it with Kelly staking for maximum edge.
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