Odds formats
How Unitley reads American odds, turns them into decimal odds, and where fractional odds fit in.
Unitley works in American odds. Every tool that takes a price takes it as American odds, and the math underneath converts it to decimal odds first. This page shows both formats and how one becomes the other, with the numbers the code returns.
American odds
An American price is a whole number of +100 or more, or −100 or less.
- A plus price is the profit on a $100 stake: +150 wins $150 on $100.
- A minus price is the stake that wins $100: −110 risks $110 to win $100.
- +100 and −100 are both even money.
The tools refuse anything else. A price between −100 and +100 comes back as an invalid_input error, and so does a price that isn't a whole number. The accepted range runs from −100000 to +1000000. Here is the REST answer for a price of 50:
{
"error": {
"code": "invalid_input",
"message": "americanOdds: American odds must be +100 or more, or -100 or less.",
"issues": [
{
"path": "americanOdds",
"message": "American odds must be +100 or more, or -100 or less."
}
]
}
}In the console, a minus price is written with a true minus sign: −110. In JSON it is a plain number, -110.
Decimal odds
A decimal price is the total return for every 1 staked, stake included. A $100 bet at 2.5 returns $250: $150 profit plus the $100 back.
American to decimal
- A plus price: decimal = 1 + American ÷ 100.
- A minus price: decimal = 1 + 100 ÷ the price without its sign.
| American | Decimal (exact) | Shown as |
|---|---|---|
| +150 | 2.5 | 2.50 |
| +200 | 3 | 3.00 |
| +100 or −100 | 2 | 2.00 |
| −110 | 1.9090909090909092 | 1.91 |
| −150 | 1.6666666666666665 | 1.67 |
| −200 | 1.5 | 1.50 |
Decimal to American
- Decimal 2.0 or more: American = (decimal − 1) × 100, a plus price.
- Below 2.0: American = −100 ÷ (decimal − 1), a minus price.
The math keeps the exact answer. Unitley rounds it to a whole number only when it shows the price, with halves rounded away from zero. Even money always reads +100.
| Decimal | Exact American | Shown as |
|---|---|---|
| 2.5 | 150 | +150 |
| 3.0 | 200 | +200 |
| 1.909 | −110.011… | −110 |
| 1.667 | −149.925… | −150 |
| 1.43 | −232.558… | −233 |
Fractional odds
Fractional odds show profit over stake: 3/2 wins $3 for every $2 staked. The MCP tools and the REST API don't take or return fractional odds.
The odds converter on the Unitley site does. It finds the closest fraction with a bottom number of 100 or less, so −110 becomes 10/11, +150 becomes 3/2 and −150 becomes 2/3. When no such fraction is exact, it shows the nearest one marked with ≈.
In the tools
calc_implied_probability takes americanOdds and returns the same price as decimalOdds, along with the chance it implies. For −110 it returns a decimalOdds of 1.9090909090909092. See Implied probability for the full answer.
The odds tools return prices the same way. In get_game_odds, each outcome carries FanDuel's American price, and fairAmericanOdds is rounded to a whole number.
For a walk through moneylines, spreads and totals in plain terms, read How to read odds.