Tools / Odds Converter
Odds Converter
American, decimal, fractional, implied probability, market price — type into any field and the rest update live. Because every odds format is the same thing wearing a different coat: a probability.
How to read each format
Every format answers the same question — how likely is this? — with different arithmetic. Here's each one decoded, using +150 as the running example.
American (moneyline)
+150 means a $100 bet wins $150. −200 means you must risk $200 to win $100. Positive = underdog, negative = favorite.
Decimal
2.50 is your total return per $1 staked — stake included. The bigger the number, the less likely the outcome. Standard in Europe.
Fractional
3/2 reads "three to two": win $3 for every $2 staked. The UK classic. Add the two numbers for the denominator.
Market price
On a prediction market, YES on a 40% event trades at 40¢ and pays $1 if it happens. No decoder ring needed — the price is the probability.
Quick reference
Common American odds and what they actually say.
| American | Decimal | Fractional | Implied prob. | Market price |
|---|---|---|---|---|
| +500 | 6.00 | 5/1 | 16.7% | 17¢ |
| +300 | 4.00 | 3/1 | 25.0% | 25¢ |
| +200 | 3.00 | 2/1 | 33.3% | 33¢ |
| +150 | 2.50 | 3/2 | 40.0% | 40¢ |
| +100 (EVEN) | 2.00 | 1/1 | 50.0% | 50¢ |
| −110 | 1.91 | 10/11 | 52.4% | 52¢ |
| −150 | 1.67 | 2/3 | 60.0% | 60¢ |
| −200 | 1.50 | 1/2 | 66.7% | 67¢ |
| −300 | 1.33 | 1/3 | 75.0% | 75¢ |
| −500 | 1.20 | 1/5 | 83.3% | 83¢ |
Why sportsbook odds always add up to more than 100%
Convert both sides of any sportsbook line and they sum past 100%. The overage is the vig — the bookmaker's margin, baked into every price. On a prediction market, YES + NO trade at roughly $1.00 combined: what you see is closer to the real probability. Try it — edit the two moneylines.
Sportsbook has vig
Prediction market no vig priced in
Right column shows the de-vigged fair line — what the sportsbook's own numbers imply once the margin is stripped out. Prediction markets quote you this directly.
Questions people ask
What do +150 odds mean?+–
+150 means a $100 stake returns $150 in winnings — and it implies a 40% chance of the event happening (100 ÷ 250). On a prediction market, the same outlook is simply a 40¢ price.
How do I convert odds to probability?+–
For positive American odds: 100 ÷ (odds + 100). For negative: |odds| ÷ (|odds| + 100). For decimal odds: 1 ÷ odds. For fractional a/b: b ÷ (a + b). Or type them into the converter above.
Why don't implied probabilities add up to 100% at a sportsbook?+–
Because the bookmaker's margin (vig) is baked into both sides. A standard -110/-110 line implies 104.8% — the extra 4.8% is what the book keeps over time regardless of the outcome.
Is a prediction-market price the same as implied probability?+–
Effectively yes — a YES contract at 40¢ pays $1 if the event happens, so the price is the market's probability. Small gaps from fees and spread exist, but there's no built-in bookmaker margin.
Which odds format should I use?+–
Whichever you'll actually reason in. Our take: probabilities. "40%" invites you to ask whether the real chance is higher or lower — which is the whole game — while "+150" mostly invites mental arithmetic.
Skip the conversion. Trade the probability.
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