Odds Converter: Decimal, Fractional, American & Implied Probability
Type odds in any format and convert instantly. Then use the value checker below to see whether a price is actually worth taking - the question that matters more than the format.
Convert odds between formats
Value checker: should you take this price?
How implied probability works
Every price is a probability in disguise. Decimal odds of $2.00 imply a 50% chance, $1.50 implies 67%, and $4.00 implies 25%. The formula is simple: implied probability = 100 ÷ decimal odds. When you compare your own estimate of a team's chance against the implied probability, you are doing what professional bettors call finding an edge.
One catch: bookmaker prices across all outcomes add to more than 100%. That extra is the margin (vig). On a typical NRL head-to-head market the total is 104-106%, meaning roughly 2-3% of each price is margin, not probability. That is why beating the market consistently is hard, and why line shopping between bookmakers matters.
Quick reference table
| Decimal | Fractional | American | Implied % |
|---|---|---|---|
| 1.20 | 1/5 | -500 | 83.3% |
| 1.50 | 1/2 | -200 | 66.7% |
| 1.80 | 4/5 | -125 | 55.6% |
| 1.90 | 9/10 | -111 | 52.6% |
| 2.00 | 1/1 (evens) | +100 | 50.0% |
| 2.50 | 6/4 | +150 | 40.0% |
| 3.00 | 2/1 | +200 | 33.3% |
| 5.00 | 4/1 | +400 | 20.0% |
| 10.00 | 9/1 | +900 | 10.0% |
More free betting tools
FAQ
How do I convert American odds to decimal?
For positive American odds (+150): decimal = (american ÷ 100) + 1, so +150 becomes 2.50. For negative odds (-200): decimal = (100 ÷ 200) + 1 = 1.50. The converter above handles both directions automatically.
How do I convert odds to a percentage?
Divide 100 by the decimal odds. $2.50 odds = 100 ÷ 2.5 = 40%. That percentage is the implied probability - the chance the price says the outcome has, including the bookmaker's margin.
Why don't implied probabilities add up to 100%?
The excess over 100% is the bookmaker's margin. If a market totals 105%, around 5 points of probability across all outcomes is margin. To estimate the market's true probabilities, divide each implied probability by the market total - that is called removing the vig (de-vigging).
What is a good edge to bet on?
Most serious bettors want their estimated probability to beat the implied probability by at least 2-4 points before betting, because estimates carry error and the margin eats thin edges. Our Kelly calculator converts an edge into a sensible stake size.