Type any odds format — decimal, American, or fractional — and instantly see the other two plus the implied win probability. The starting point for spotting value: know what a price really means before you compare it to your own estimate.
Detected: decimal odds
Every bookmaker price is really just three different ways of writing down the same number. Decimal odds (2.50, common in Europe and on exchanges) show your total return per unit staked, including your stake back. American odds (+150 or −200, used by US books) show either the profit on a $100 bet (positive) or the stake needed to profit $100 (negative). Fractional odds (3/2, traditional in the UK) show profit relative to stake as a ratio. All three describe the exact same price — they just format it differently.
What actually matters for betting decisions isn't the format, it's the implied probability hiding underneath it: 1 divided by the decimal odds. Odds of 2.50 imply a 40% chance; −200 (decimal 1.50) implies 66.7%. Once you convert every price to implied probability, you can compare it directly against your own estimate — or against a sharp book's price — on a common scale, regardless of which format either side quotes in.
One thing implied probability from a single book's price does NOT show you: the bookmaker's built-in margin (the vig). Add up the implied probabilities of every outcome in a market and the total is always over 100% — the excess is the house edge baked into that specific price. Removing it ("devigging") is the next step after conversion, and it's why comparing raw implied probability across books, without adjusting for margin, can be misleading.
A quick reference for the prices you'll see most often — decimal, American, fractional and the implied probability behind each.
| Decimal | American | Fractional | Implied prob. |
|---|---|---|---|
| 1.20 | -500 | 1/5 | 83.3% |
| 1.50 | -200 | 1/2 | 66.7% |
| 1.91 | -110 | 10/11 | 52.4% |
| 2.00 | +100 | 1/1 | 50.0% |
| 2.50 | +150 | 3/2 | 40.0% |
| 3.00 | +200 | 2/1 | 33.3% |
| 3.50 | +250 | 5/2 | 28.6% |
| 4.00 | +300 | 3/1 | 25.0% |
| 5.00 | +400 | 4/1 | 20.0% |
| 7.00 | +600 | 6/1 | 14.3% |
| 10.00 | +900 | 9/1 | 10.0% |
| 15.00 | +1400 | 14/1 | 6.7% |
For positive American odds, decimal = 1 + (american / 100) — so +150 becomes 1 + 1.50 = 2.50. For negative American odds, decimal = 1 + (100 / |american|) — so −200 becomes 1 + 0.50 = 1.50. The odds converter above does this instantly for any input.
Implied probability is the win chance a betting price corresponds to: 1 divided by the decimal odds, expressed as a percentage. Odds of 2.50 imply a 40% chance of winning. It's the number you actually compare against your own probability estimate (or a sharper book's price) to find value — not the raw odds format.
Because every price includes the bookmaker's margin, known as the vig or overround. Add up the implied probability of every outcome in a market — home/draw/away, or over/under — and it will always sum to more than 100%; the excess is the house's built-in edge. Removing it ("devigging") reveals the market's true probability estimate.