Guides

The overround explained with arithmetic you can check: how to convert odds into implied probability, why those probabilities add up to more than 100%, and what the difference between a 2.5% and a 6% book does to a season's staking.

The three odds formats explained, how to convert between them in one step each, and why decimal is the only sensible format for comparing prices between bookmakers.

An each-way bet is two bets: one to win, one to place. Here is how the place part is priced, what "1/4 odds, 3 places" means, when a placed bet still loses money, and how to tell whether the each-way terms on offer are any good.

An accumulator multiplies the odds of every leg. It also multiplies the bookmaker's margin. A 5% edge on one match becomes 28% on a five-fold and 63% on a ten-fold. Here is the arithmetic, a table for one to ten legs, and what it means for how you bet.

How stake limiting and account closure actually work, why the recreational-customer business model produces them, which operators do it least, and what a bettor can realistically do in response.

Best odds guaranteed pays you the bigger starting price if it beats the price you took — but only on UK and Irish racing, only from a set time on race day, and at Sky Bet only after a weekly turnover qualifier most casual punters never clear. Here is what each operator actually promises.

How backing and laying works, why commission on winnings is structurally different from a margin charged on every bet, and the arithmetic of when each is actually cheaper.

What a gambling licence gives you in practice, how to verify one on the regulator's own register in two minutes, and the real difference between a tier-one licence and a Curaçao one.

The tools every licensed operator must give you, how national self-exclusion schemes work, what problem gambling actually looks like, and where to find free confidential help.

What a free bet returns, what it is worth on average, and the odds that make the most of it.

Returns for win and place at 1/4 or 1/5 terms, Rule 4 deductions, and what the place terms are worth.

Combined odds and returns for up to 10 legs, and how the bookmaker's margin compounds across them.

The exact lay stake and liability for a back-and-lay bet, with exchange commission properly accounted for.