A six-runner race where implied probabilities sum to 112% has a 12% overround\u2014meaning the bookmaker’s theoretical margin is 12% before any punter places a bet. But without calculating implied probability, non gamstop betting sites<\/a> you cannot begin to answer that question systematically. For odds comparison across multiple bookmakers, decimal format saves time and reduces errors. This format dominates betting exchanges and has become standard on many online platforms, particularly for European customers. At 4\/6 (sometimes written 4-6), you need to stake \u00a36 to win \u00a34 profit, returning \u00a310 total from a \u00a36 stake. Before diving into specific strategies, we need to establish fluency with the formats you will encounter.<\/p>\n On feature races \u2014 the Champion Hurdle, the Gold Cup, the Grand National, Saturday afternoon handicaps at major tracks \u2014 the exchange market is deep enough that you can back at the displayed price without difficulty. Over time, backing at exchange odds rather than bookmaker odds produces a measurably higher return on investment, assuming you can find liquidity on your chosen market. Where a bookmaker might offer 5\/1 on a horse with a 120 per cent book, the exchange might show 5.5 (or 9\/2 in fractional terms) on the same runner with a total market overround of 103 per cent. The overround on the Grand National ante-post market can reach as high as 180 per cent \u2014 a level that would be considered predatory in any raceday market.<\/p>\n