Odds Converter
Enter a quote in whatever format you have it -- American, decimal, fractional, or a prediction-market price in cents -- and see it in every other format at once, plus what it implies about the probability.
Convert from
Must be at or beyond +100/-100 -- there's no such thing as American odds of, say, +50.
American
-110
Decimal
1.909
Fractional
10/11
Implied probability
52.38%
Contract price
52.4¢
Contracts per $100
191
at this price, to win $1 each
Reference table
| Quote | American | Decimal | Fractional | Implied | Price |
|---|---|---|---|---|---|
| American -110 | -110 | 1.91 | 10/11 | 52.38% | 52.4¢ |
| American +150 | +150 | 2.50 | 3/2 | 40.00% | 40.0¢ |
| Decimal 2.50 | +150 | 2.50 | 3/2 | 40.00% | 40.0¢ |
| Fractional 3/1 | +300 | 4.00 | 3/1 | 25.00% | 25.0¢ |
| Contract price 65¢ | -186 | 1.54 | 7/13 | 65.00% | 65.0¢ |
How the conversions work
Every format on this page -- American odds, decimal odds, fractional odds, a prediction-market contract price in cents, and implied probability -- describes the exact same underlying number. Decimal odds are the anchor: they're the total payout per $1 staked, including your stake back, so a decimal of 1.909 means a $1 bet returns $1.909 if it wins. Every other format is a straightforward transform of that one number.
Implied probability is just 1 divided by the decimal price. A decimal odds of 1.909 (American -110) implies a 52.38% chance -- and a shorter decimal of 2.50 (American +150) implies a lower 40.00% chance. Lower decimal odds always mean a shorter price, i.e. a more heavily favored outcome.
American odds split at the 50/50 line: a positive number (+150) shows what a $100 stake wins on an underdog; a negative number (-110) shows what you'd need to stake to win $100 on a favorite. Fractional odds (10/11 for a -110 favorite) show net winnings per unit staked, British-bookmaker style -- and because most real prices don't land on a clean ratio, this page shows the closest simple fraction rather than an exact repeating decimal.
Contract price is the odd one out, and the simplest: a prediction-market contract that costs 52.4¢ and pays $1 if it resolves YES is, by construction, pricing that outcome at 52.4%. There's no conversion step at all -- the price already is the probability, expressed in cents instead of a percent sign.
Frequently Asked Questions
Why do American odds skip everything between -99 and +99?
Because American odds describe a ratio relative to a $100 stake, and a fair coin flip -- 50/50 -- already sits at the boundary: +100 (win $100 on a $100 bet) and -100 (bet $100 to win $100) both describe the exact same 2.00 decimal price. Anything less lopsided than a coin flip doesn't correspond to a real number in this format, so the notation jumps straight from -100 to +100 with nothing valid in between.
Why does 65¢ convert to -186, not -185.7?
American odds are conventionally shown as a whole number. The exact value from a 1.5385 decimal price is -185.71, which rounds to -186. Sportsbooks round the same way, so -186 is what you'd actually see quoted next to a 65% implied favorite.
Is a prediction-market contract price the same thing as odds?
It's a different notation for the same idea. A contract priced at 65¢ isn't 65% likely because of some separate odds calculation -- the price IS the market's probability estimate, because the contract pays exactly $1 if it happens and $0 if it doesn't. That's simpler than betting odds, which quote a payout ratio rather than a probability directly, which is exactly why this page converts between the two.
Why does the fractional column sometimes show a big denominator?
Fractional odds only look clean when the underlying probability lands on a simple ratio -- 3/1, 10/11, 4/5. A contract price in whole cents always has an exact fraction with a denominator under 100 (a 65¢ price is exactly 35/65, reduced to 7/13), so it's decimal or American odds that aren't derived from a round cent price where things get messy: a decimal of 1.91 has no clean ratio at all, so this converter shows the closest simple fraction instead -- 91/100, capped at a two-digit denominator so it stays readable. That approximation is standard practice -- it's what odds boards do too -- and it's accurate to within a fraction of a percent.
Which format should I actually use?
Whichever the platform quotes. Sportsbooks in the US default to American, most of the rest of the world uses decimal, UK books often use fractional, and prediction markets like Kalshi and Polymarket price contracts directly in cents. None of them is more 'correct' -- they're just different labels on the same implied probability, which is why this page treats probability as the common unit underneath all four.
SidebySideCalc's prediction-market calculators apply standard odds, probability, and bankroll-sizing math to the numbers you enter -- they are not trading advice. Prediction markets carry real risk of loss and may be restricted or unavailable in some jurisdictions; nothing here names or endorses a specific trading venue.