Odds Converter
Convert between American, decimal and fractional odds and implied probability in one view, including Polymarket prices. Updates as you type.
How to use this converter
Type a price in any notation. -110, 1.91, 10/11, 52.4% and 52¢ all describe the same chance of winning, and the converter shows every other format at once. The format selector only matters for bare numbers: 150 is read as +150 in American mode, as 150.00 in decimal mode and as an error in probability mode.
Switch on exchange commission to see the effective odds after an exchange takes its cut of winnings, and the win rate you need to break even at that price. Paste-a-list mode converts one price per line, which is handy when you copy a whole market out of a sportsbook.
The conversion formulas
Decimal odds are the hub every other format goes through. They are the total return per unit staked, including the stake, so 1.909 returns 1.909 for every 1.00 bet.
- American to decimal. Negative prices show the stake needed to win 100:
decimal = 1 + 100 / |american|, so -110 is1 + 100 / 110 = 1.909. Positive prices show the profit on 100:decimal = 1 + american / 100, so +150 is 2.50. - Decimal to American. For decimal odds of 2.00 or more,
american = (decimal − 1) × 100; below 2.00,american = −100 / (decimal − 1). 2.50 is +150 and 1.909 is -110. - Decimal to fractional. Subtract one and reduce the fraction: 1.909 is 0.909, which is 10/11; 2.50 is 3/2. Fractional odds show profit relative to stake, so 10/11 wins 10 for every 11 staked.
- Decimal to implied probability.
probability = 1 / decimal, so 1.909 is 52.38% and 2.50 is 40.00%. - Polymarket price. The cost in cents of a share that pays $1.00, which equals the implied probability: -110 is 52¢, +150 is 40¢.
Following one price the whole way round: -110 → 1.909 → 10/11 → 52.38% → 52¢. The converter keeps the exact value internally and rounds only when it displays, which is why -110 shows as 1.909 rather than the 1.91 a bookmaker prints.
Why +100 and -100 are the same price
Even money is decimal 2.00: stake 100 to win 100. Written as a positive American price that is +100 (profit of 100 on 100); written as a negative price it is -100 (stake 100 to win 100). They are one price with two spellings, and the converter always shows the canonical +100. The same is true of any price at exactly 2.00, which is why American odds jump from -105 straight past ±100 to +105.
Common odds conversions
| American | Decimal | Fractional | Implied probability |
|---|---|---|---|
| -1,000 | 1.100 | 1/10 | 90.91% |
| -500 | 1.200 | 1/5 | 83.33% |
| -400 | 1.250 | 1/4 | 80.00% |
| -300 | 1.333 | 1/3 | 75.00% |
| -250 | 1.400 | 2/5 | 71.43% |
| -200 | 1.500 | 1/2 | 66.67% |
| -150 | 1.667 | 2/3 | 60.00% |
| -120 | 1.833 | 5/6 | 54.55% |
| -110 | 1.909 | 10/11 | 52.38% |
| -105 | 1.952 | 20/21 | 51.22% |
| +100 | 2.000 | 1/1 | 50.00% |
| +105 | 2.050 | 21/20 | 48.78% |
| +110 | 2.100 | 11/10 | 47.62% |
| +120 | 2.200 | 6/5 | 45.45% |
| +150 | 2.500 | 3/2 | 40.00% |
| +200 | 3.000 | 2/1 | 33.33% |
| +250 | 3.500 | 5/2 | 28.57% |
| +300 | 4.000 | 3/1 | 25.00% |
| +400 | 5.000 | 4/1 | 20.00% |
| +500 | 6.000 | 5/1 | 16.67% |
| +1,000 | 11.000 | 10/1 | 9.09% |
Every American price from -10000 to +10000 has its own page with payouts, exchange odds and neighbouring prices; start from the American odds hub or the decimal and fractional hubs.
Implied probability and why a market sums to more than 100%
Implied probability is what the price would be worth if the bookmaker took no margin. Add up the implied probabilities of every outcome in a market and the total exceeds 100%: a -110 / -110 market implies 52.38% on each side, 104.76% in total. The extra 4.76% is the overround, the bookmaker's margin expressed in the prices. It means the implied probability of a single price always overstates the outcome's real chance a little.
To recover probabilities that sum to 100% you need every price in the market and a method for spreading the margin. That is what the devig calculator does, with five methods to choose from. Once you have a fair probability, the EV & Kelly calculator compares it with any price to find the edge and a stake.
Frequently asked questions
Why does -110 not convert to exactly 1.91?
-110 is exactly 1.9091 in decimal. Bookmakers display 1.91 because prices are rounded to two places, and 1.91 converts back to -109.9, not -110. This converter keeps the exact value internally and rounds only for display.
What is the difference between +100 and -100?
Nothing. Both mean even money (decimal 2.00, 1/1). The converter shows the canonical +100.
How do I convert odds to probability?
Divide one by the decimal odds. 2.50 is 1 / 2.50 = 40%. For American odds convert to decimal first, or use the rule of thumb: a negative price -X is X / (X + 100), a positive price +Y is 100 / (Y + 100). -150 is 60%, +200 is 33.3%.
Can I convert Polymarket prices to sportsbook odds?
Yes. Enter the price in cents with the Polymarket format selected, or type 64¢. A 64¢ YES share is decimal 1.5625, or -178 in American odds. The Polymarket converter shows both sides of a market and the spread between them.
What are the odds after exchange commission?
Turn on commission and pick the exchange. A back bet at 2.00 with 5% commission on net winnings is worth 1.95 after the exchange's cut, and you need to win 51.28% of the time to break even. The commission calculator goes deeper, including lay bets and turnover charges.