Odds Converter: Decimal, Fractional and American, Side by Side

Decimal, fractional and American odds all describe the exact same underlying price — the same chance of winning and the same payout on the same stake — written down three different ways for three different regional audiences. Our odds converter below turns any one format into the other two instantly, and the rest of this page walks through the maths so you understand what each number is actually telling you, not just what it converts to.

How the three formats relate to each other

Decimal odds are the simplest to reason about because they already include your stake: multiply your stake by the decimal figure and you get your total return, stake included. Odds of 2.50 on a $10 bet return $25 in total — $15 profit plus your original $10 back. Decimal is the standard format across continental Europe, Australia and most of Asia, and it's the default format most betting exchanges and modern sportsbooks use, precisely because the multiplication is so direct.

Fractional odds, the traditional format in UK and Irish betting shops and still the default on many horse-racing boards, describe pure profit relative to stake rather than total return. Odds of 3/2 mean you profit $3 for every $2 you stake — bet $2, and a win returns $5 in total ($3 profit plus your $2 stake back). Converting decimal to fractional is just decimal odds minus one, expressed as a reduced fraction: 2.50 − 1 = 1.50, which reduces to 3/2 — exactly what the tool above shows if you type 2.50 into the decimal field.

American odds (also called moneyline odds) are the standard in the United States and split into two ranges around an even-money price. A negative number tells you how much you'd need to stake to profit $100 — odds of -200 mean staking $200 to win $100 profit, for a $300 total return. A positive number tells you how much profit a $100 stake would earn — odds of +150 mean a $100 stake profits $150, for a $250 total return. The crossover point is decimal odds of exactly 2.00, where American odds sit at precisely +100 or -100 (evens, or 1/1 in fractional terms).

The exact conversion formulas

Decimal to American: if decimal odds are 2.00 or higher, American odds equal (decimal − 1) × 100. If decimal odds sit below 2.00, American odds equal −100 ÷ (decimal − 1). Reverse the process to go from American back to decimal: for a positive American price, decimal odds equal (American ÷ 100) + 1; for a negative American price, decimal odds equal (100 ÷ |American|) + 1. Fractional odds convert to decimal by dividing the numerator by the denominator and adding one — 3/2 becomes (3 ÷ 2) + 1 = 2.50 — and decimal converts back to fractional by subtracting one and reducing the remaining figure to its simplest whole-number ratio.

That reduction step is the only part of odds conversion that takes real work by hand, which is exactly why a calculator earns its keep here: reducing 1.909 (from American -110) to a clean fraction by hand means finding the closest simple ratio, not just dividing two numbers, and doing it under time pressure while a price is about to move is where manual conversion mistakes creep in.

Worked examples across all three formats

Take a moderate underdog priced at 3.00 decimal. Subtract one to get 2.00, which reduces to a clean 2/1 in fractional terms — bet $1, profit $2, return $3 total. Convert the same price to American: since 3.00 sits at or above 2.00, the formula is (3.00 − 1) × 100 = +200, meaning a $100 stake profits $200. All three numbers — 3.00, 2/1 and +200 — describe one identical bet.

Now take a short-priced favourite at 1.50 decimal. Below 2.00, so the American formula is −100 ÷ (1.50 − 1) = −200: stake $200 to profit $100. In fractional terms, 1.50 − 1 = 0.50, which reduces to 1/2 — bet $2 to profit $1. Several multi-vertical operators we've reviewed pair a sportsbook alongside their casino product — W88, 1xbet, Dafabet and BK8 among them — and every one of those bet slips is doing this exact arithmetic behind the scenes every time a price updates, regardless of which of the three formats your account happens to display.

When the converted number can mislead you

The single biggest trap is assuming a converted number is somehow "truer" or more precise than the one you started with. It isn't — a correct conversion is mathematically identical to the original price, full stop. Where confusion creeps in is rounding at the display layer: bookmakers almost always post fractional and American prices as tidy, rounded figures rather than exact continuous decimals, so a genuinely precise internal price of, say, 1.9091 decimal gets rounded on the board to a clean 10/11 or -110. Convert that rounded 10/11 back to decimal and you'll land on exactly 1.909090..., which is close to but not identical to the operator's original unrounded figure — a tiny discrepancy from rounding at the source, not from any error in the conversion itself.

The second trap is bigger: converting a price between formats tells you nothing about how good a bet actually is. A cleanly converted 2.50 decimal, 3/2 fractional and +150 American are all just three faces of the same number — none of them removes the bookmaker's built-in margin, and none of them tells you your real chance of winning versus the market's implied chance. For that question, you want our implied probability calculator, which takes this exact same decimal figure and turns it into a percentage, plus a two-way tool that exposes how much margin a bookmaker has actually built in.

Putting a converted price to work

Once you've settled on a price in whichever format you're comfortable reading, the next natural questions are usually "what does this actually pay out on my stake" and, if you're combining several selections, "what does the combined price look like across all of them." Our bet calculator takes odds in any of the three formats plus your stake and returns payout, profit and implied probability in one step, while our parlay calculator handles the multiplication across multiple legs when you're building an accumulator rather than a single straight bet.

The bottom line: decimal, fractional and American odds are one price wearing three different regional outfits, and being fluent in all three means you can compare a line across sportsbooks, formats and even countries without doing mental arithmetic under time pressure. Use the calculator above whenever you need a quick, reliable conversion, and lean on our other tools once you're ready to work out what a price actually means for your stake and your real chance of winning.

Frequently Asked Questions

Which odds format should I actually use — decimal, fractional or American?

Whichever your sportsbook shows by default and you find easiest to read quickly. The three formats describe exactly the same underlying price; none is mathematically "better" than another. Decimal is the international default across most of Europe and Asia, fractional is the traditional UK and Irish format, and American (moneyline) is standard in the United States. Most sportsbook accounts let you switch the display format in your settings without changing the actual odds on offer.

Why does converting the same odds twice sometimes give a slightly different number back?

Rounding. Bookmakers usually post fractional and American odds as tidy, rounded figures — 11/10 or -110 rather than an exact continuous decimal like 1.909 — so converting a rounded fraction back to decimal, then back to a fraction again, can land a hair away from where you started. It is a display-rounding artefact, not a sign the maths is wrong, and it rarely moves your actual payout by more than a rounding unit.

Does converting odds between formats change my potential payout?

No. Decimal, fractional and American odds are three different notations for one identical price, and a correct conversion always represents the exact same payout on the exact same stake. What changes is only how that price is written down — the maths underneath, and the money that changes hands if the bet wins, stays the same regardless of which format is displayed on the slip.

Does this odds converter tell me my real chance of winning?

Only approximately, and only if you convert to a probability separately — this tool converts between odds notations, not into probability. Every price also bakes in the bookmaker's built-in margin (overround), so the raw number always overstates the true chance slightly. Our implied probability calculator, linked below, walks through both the raw number and the fairer, margin-adjusted version.