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Odds Converter
Type into any field and the other two update instantly. For informational purposes only: always confirm the exact odds and payout on your sportsbook before betting.
How betting odds work
The three formats you'll run into, and what they actually represent.
Odds are just a price on an outcome
Every set of odds is a way of pricing how likely a sportsbook thinks an outcome is, and what it'll pay out if that outcome happens. Higher odds mean a less likely outcome and a bigger payout; lower odds mean a more likely outcome and a smaller payout. The three formats below all describe the exact same underlying price, they just present it differently depending on where you're betting.
Implied probability
Every odds format converts to a percentage: the implied probability of that outcome happening, according to the price. This isn't the sportsbook's real prediction of the odds of winning; it includes their built-in margin (often called the vig or juice), which is why the implied probabilities on both sides of a single bet usually add up to a bit more than 100%.
American, Decimal, and Fractional odds explained
Same price, three different ways of writing it down.
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American odds (e.g. -110, +150)
The standard in the US. A negative number shows how much you'd need to stake to win $100 (-110 means bet $110 to win $100). A positive number shows how much you'd win on a $100 stake (+150 means bet $100 to win $150). Anything shorter than even money is negative; anything longer than even money is positive.
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Decimal odds (e.g. 1.91, 2.50)
The standard across Europe, Canada, and Australia. Multiply your stake by the decimal number to get your total return, winnings included. A $100 stake at 2.50 returns $250 total: $150 profit plus your original $100 back.
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Fractional odds (e.g. 10/11, 3/2)
The standard in the UK and Ireland. Reads as profit relative to stake: 3/2 means you win $3 for every $2 staked, on top of getting your stake back. 10/11 means a bit less than even stakes: bet $11 to win $10 in profit.
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They all convert to the same implied probability
-110 American, 1.91 Decimal, and 10/11 Fractional are all the same price, just written three different ways, and all three imply the same roughly 52.4% probability. That's the number this tool is really doing the work to show you.
Reading odds like a bettor
A few things worth understanding once you're comfortable converting between formats.
The vig is built into every line
Add up the implied probabilities on both sides of almost any two-way bet and you'll get something over 100%, often around 104-107%. That gap is the sportsbook's built-in edge. It's not a sign anything's wrong with the odds; it's just how the book makes money regardless of which side wins.
Shopping for the best number matters
The same game can carry slightly different odds at different sportsbooks. Since the format doesn't change the underlying price, converting to a single format (decimal is usually easiest for quick comparison) makes it simple to see which book is actually offering the better number before you place a bet.
Bigger favorites don't mean a bigger implied edge for you
A heavily negative American numbet like -400 has a high implied probability (around 80%) but a small payout relative to stake. Long positive numbers like +400 have a low implied probability (around 20%) but pay out big if they hit. Neither is inherently the "smarter" bet; it depends entirely on whether you think the real probability is better than what's implied.
Odds converter FAQ
Is this odds converter free?
Yes. It runs entirely in your browser, needs no account, and nothing you type is saved or sent anywhere.
Why do my implied probabilities add up to more than 100%?
That's expected. Sportsbooks build a margin (the vig, or juice) into their odds on both sides of a bet, so the true implied probabilities always overshoot 100% by a few percentage points. It's not a bug in the conversion, it's how the book prices its edge.
What's the difference between +150 and -150?
+150 means a $100 bet wins $150 profit (a longer-odds underdog). -150 means you'd need to bet $150 to win $100 profit (a shorter-odds favorite). They convert to different implied probabilities: about 40% for +150 and about 60% for -150.
Why doesn't a decimal like 1.91 convert back to an exact fraction?
It does, approximately. This tool finds the simplest fraction that's a close match (the same approach sportsbooks themselves use), so 1.91 correctly maps to 10/11 rather than an ugly exact fraction like 91/100. Small rounding differences between formats are normal in the industry.
Does Gamdom offer sports betting?
Gamdom's platform includes a sportsbook section alongside its casino Originals and slots. Coverage, markets, and odds formats offered can change, so confirm the current details directly on Gamdom before relying on this tool for a specific bet there.
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This converter is just for understanding the numbers. Head to Gamdom to see live odds and current markets before you bet. Building a parlay? Try our Bet Slip Calculator too.