Guides
One question per guide, answered with numbers computed by code. New guides are added regularly.
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The bookmaker's margin
What the overround is and how to remove it.
What parlays cost
How the margin compounds with every leg.
Kelly staking
How much to stake when an edge is real.
From expected goals to fair odds: the Poisson model for one football match
Learn how expected goals determine match probabilities and fair odds using the Poisson model for football betting.
Asian handicap quarter lines: how -0.25 and -0.75 split your stake
Quarter Asian handicap lines split stakes into halves, causing partial refunds or wins on specific match outcomes.
Dutching three selections: the same profit whichever wins, and a total loss if none does
Dutching splits stakes by implied probability to equalize returns, though the bookmaker margin still reduces overall value.
Overbetting: why twice the Kelly stake grows nothing
Staking beyond the Kelly optimum reduces expected growth because losses impact the bankroll more heavily than wins.
Free bets: why you keep most of one at long odds and under half at short odds
Long odds preserve more value from a non-returnable free bet than short odds due to how winnings exclude the stake.
Each-way bets: how the place terms turn into money
An each-way bet splits your stake into win and place parts, with the place fraction determining the separate payout.
Two-way arbitrage: when the best prices add up to less than 100%
Two-way arbitrage locks in profit when implied probabilities sum to less than the baseline, requiring precise stake splitting.
Lay betting: stake, liability and the result either way
How lay betting balances outcomes against a back bet, covering stake size, liability, and the small net loss from commission.
Hedging a bet: the stake that locks in the same result
A hedge locks in profit by betting the opposite side, paying the margin twice to remove uncertainty from the outcome.
Expected value and break-even probability: the two numbers behind every bet
Learn how expected value and break-even probability interact, using the key figures to show how estimates guide long-term betting outcomes.
Football's three-way market: finding the margin and the fair odds
Learn how to calculate the bookmaker margin in football markets and derive fair odds from the offered prices.
The ten-leg parlay: the jackpot price and the real chance of hitting it
A ten-leg parlay of coin flips wins rarely and pays less than fair odds, creating a significant house edge over many bets.
Half Kelly: most of the growth for half the stake
Half Kelly offers most of the growth with smaller swings, but requires a real edge and accurate probabilities to work effectively.
What -110 means: the vig hidden in the standard betting line
Learn how standard betting odds translate to decimal values and why implied probabilities exceed the total, creating a house margin.
Why parlays cost more: the bookmaker's margin compounds with every leg
Each leg in a parlay adds the bookmaker's margin, causing the total cost to rise sharply as more selections are combined.
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