Implied Probability and the Bookmaker’s Margin
Learn how to turn odds into implied probabilities, calculate an overround and understand what the figures do—and do not—tell you.
Johny Atwood commentated on sports matches before turning to writing. He now explains odds, bet types and betting rules in plain English.
Before he started writing, Johny Atwood commentated on sports matches. Commentary is work done in real time: you describe what is happening as it happens, explain why a moment matters and keep listeners with you when the game turns. Johny now writes the guides on Sportsimba, and that habit of explaining a game while it unfolds is the one he brings to every page.
Anyone who follows sport knows how often the words around a game get in the way of the game itself. Odds are quoted as fractions on one screen and decimals on the next, a market is suspended in the middle of a match with no explanation, and a bet slip can use three different terms for one idea. Johny's aim is to take those words one at a time and explain them in plain English, the way a commentator explains an offside call or a change of shape to someone who has just tuned in.
Every guide starts with the question a reader actually has, such as how an each-way bet pays out or what "stake not returned" means on a free bet. Johny answers it directly, then works through an example that is clearly labelled as an example, with the arithmetic shown so you can check it yourself. Where a rule depends on the bookmaker, he says so instead of pretending there is a single answer.
Johny does not give tips, predict results or tell readers which bets to place. A commentator describes the match; he does not decide it. The same line holds on Sportsimba: the guides explain how betting works so that readers understand what they are agreeing to, and they never promise winnings. If you choose to bet, set a limit you are comfortable losing and take a break when it stops being fun.
If something in one of his guides is unclear or wrong, write to the address on the contact page with the page and the sentence, and it will be looked at.
Guide
Learn how to turn odds into implied probabilities, calculate an overround and understand what the figures do—and do not—tell you.
Guide
Learn how a single differs from a multiple, how to calculate a straightforward return and what happens when a selection is void.
Guide
Learn how withdrawals, ties and void bets can affect settlement, with worked arithmetic and a checklist for the rules.
Guide
Understand how a bet qualifies for a promotion, why settlement matters and what to check before betting.
Guide
Understand common betting terms, from accumulators and each-way bets to non-runners and void selections, with a worked example.
Guide
An each-way bet combines equal win and place stakes. Learn how place terms affect settlement and calculate the possible returns.