Odds Converter

How odds formats relate

Every odds format encodes the same two numbers: the implied probability of an outcome, and the payout multiple if it happens. Decimal odds are the simplest to convert from — multiply your stake by the decimal value to get your total payout (stake included). Fractional, American, and the Asian formats are all just different conventions for presenting that same multiple. None of them is mathematically "better" than another; each simply grew out of a different regional betting market, and sportsbooks display whichever format their local audience expects.

Fractional odds (e.g. 5/1) show profit relative to stake — a 5/1 bet returns five units of profit per one unit staked, plus your stake back. American odds separate favorites and underdogs by sign: a bet at -200 requires staking 200 to profit 100 (a favorite), while a bet at +200 profits 200 on a 100 stake (an underdog). Hong Kong odds are effectively the same profit ratio as fractional but expressed as a single decimal-like number. Malay and Indonesian odds flip in sign depending on whether the price represents a favorite or an underdog, which is exactly why they’re the two formats bettors most often convert rather than read directly.

Converting odds to implied probability

Every odds format can be converted to an implied probability — the chance of that outcome the market is pricing in, before the bookmaker’s margin is stripped out. For decimal odds, implied probability = 1 ÷ decimal odds. Odds of 2.50, for example, imply a 40% chance (1 ÷ 2.50 = 0.40). For American odds, a negative price’s implied probability is |price| ÷ (|price| + 100), while a positive price’s is 100 ÷ (price + 100). Converting every format to a common decimal basis first — which is what this tool does under the hood — makes it far easier to compare probability and value across markets quoted in different conventions.

It’s worth remembering that implied probability from a single sportsbook’s odds always overstates the true chance of the outcome, because the odds bake in the bookmaker’s margin (the "vig" or "juice") on top of the fair price. Summing the implied probabilities of every outcome in a two- or three-way market will typically add up to more than 100% — the excess over 100% is the book’s built-in edge. Our No-Vig Odds Calculator strips that margin back out to estimate the fair price behind a quoted line.

A worked conversion example

Suppose a UK sportsbook quotes 7/2 fractional odds on a football match outcome. Converting to decimal: 7 ÷ 2 = 3.5, plus 1 (to include the returned stake) = 4.50 decimal. Converting that decimal to American odds: since decimal odds are above 2.00, the formula is (decimal − 1) × 100 = 350, shown as +350. The implied probability is 1 ÷ 4.50 ≈ 22.2%. All three numbers — 7/2, 4.50, and +350 — describe the exact same bet; only the notation changes. This is exactly the kind of cross-check this tool exists for: confirming that odds quoted in an unfamiliar format really do match the price you think you’re seeing before you stake money on it.

Why bettors convert odds at all

Beyond simple curiosity, converting odds between formats serves two practical purposes. First, it lets you compare a price across sportsbooks that each display odds in a different regional format — an operator showing American odds and one showing decimal odds might actually be offering the same, or meaningfully different, prices on the same event, and you can’t tell which without converting both to a common format first. Second, it’s a prerequisite for other betting math: arbitrage, expected value, Kelly staking, and no-vig fair odds all operate on decimal odds or implied probability under the hood, so converting an unfamiliar quoted format into decimal is usually the first step before running any of those calculations by hand.

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