Three formats, one price
A bet’s odds are its price tag: how much a winning bet pays relative to what you stake. Sportsbooks around the world write that price three different ways.
American odds, the plus and minus numbers on US sportsbooks, like +150 or -200.
Decimal odds, the format used across Europe, Canada, Australia and most of the rest of the world, like 2.50 or 1.50.
Fractional odds, the traditional British and Irish bookmaker style, like 6/4 or 1/2.
All three describe the same payout. Once you can read one and convert to the others, two lines of arithmetic, you can compare any two prices at any two sportsbooks and see which is better. That habit, called line shopping, is the most practical edge available to a regular bettor. Our glossary has one-line definitions if you want the terms first; this guide has the math.
American odds: the plus and the minus
American odds are always written with a plus or minus sign, and both refer to a $100 stake.
- A plus price tells you what a $100 bet wins. +150 means a $100 stake returns $150 in profit, plus the $100 stake, $250 in total. Plus prices go to underdogs: the bigger the number, the bigger the payout and the less likely the book thinks the outcome is.
- A minus price tells you what you must stake to win $100. -200 means a $200 stake wins $100. If you bet $100 at -200 instead, you win $50 and get $150 back. Minus prices go to favorites: the bigger the number, the more you risk to win the same $100.
Two quick examples:
- +150: a $100 bet wins $150 (total return $250). A $50 bet wins $75.
- -200: a $100 bet wins $50 (total return $150). A $500 bet wins $250.
The pattern in one line: plus prices pay more than your stake, minus prices pay less.
Decimal odds: the international standard
Decimal odds show the total return per unit staked, including your stake. Multiply your stake by the decimal and you have your total return.
- 2.50: a $100 bet returns $250: $150 profit plus the $100 stake.
- 1.50: a $100 bet returns $150: $50 profit plus the $100 stake.
Because the stake is baked in, decimal odds are the easiest format to multiply, which matters when you look at parlays. If you’ve seen odds like 1.91 or 2.50 on an international site, that’s decimal.
Fractional odds: the old-school format
Fractional odds show profit only, expressed as a fraction: 6/4 means you win $6 for every $4 staked.
- 6/4: stake $100, win $150 (6 ÷ 4 = 1.5 times the stake). Total return $250.
- 1/2: stake $100, win $50 (0.5 times the stake). Total return $150.
Fractional odds remain standard in UK and Irish racing coverage. 6/4 is exactly the same price as 3/2, and the same price as +150 in American odds or 2.50 in decimal. 1/2 is the same as -200 or 1.50.
The conversion table
| American | Decimal | Fractional | Return on $100 | Implied probability |
|---|---|---|---|---|
| +150 | 2.50 | 6/4 (or 3/2) | $250 | 40.0% |
| -200 | 1.50 | 1/2 | $150 | 66.7% |
| -110 | 1.91 | 10/11 | $190.91 | 52.4% |
| +170 | 2.70 | 17/10 | $270 | 37.0% |
| +100 | 2.00 | 1/1 (evens) | $200 | 50.0% |
Read the table left to right and you’re reading the same price in four languages. The last column, implied probability, is the part most bettors skip, and it’s the most useful. More on it below.
Converting by hand: the formulas
American to decimal. For plus odds, divide by 100 and add 1: +150 → 1.50 + 1 = 2.50. For minus odds, divide 100 by the odds and add 1: -200 → 0.50 + 1 = 1.50.
Decimal to American. If the decimal is 2.00 or higher, subtract 1, multiply by 100 and add a plus sign: 2.50 → 1.50 × 100 = +150. If it’s below 2.00, divide 100 by the decimal minus 1 and add a minus sign: 1.50 → 100 ÷ 0.50 = -200.
Fractional to decimal. Divide the top number by the bottom and add 1: 6/4 → 1.50 + 1 = 2.50; 1/2 → 0.50 + 1 = 1.50.
Decimal to fractional. Subtract 1 and write the result as a fraction: 2.50 → 1.50 = 3/2 (same as 6/4); 1.50 → 0.50 = 1/2.
Fractional to American. If the fraction is 1 or more, multiply by 100 for a plus price: 6/4 → 1.50 × 100 = +150. If it’s below 1, divide 100 by the fraction for a minus price: 1/2 → 100 ÷ 0.50 = -200.
Worked examples
The underdog, three ways. A book prices an underdog at +150. Decimal: 150 ÷ 100 + 1 = 2.50. Fractional: 150/100 = 3/2, commonly written 6/4. A $100 bet returns $250.
The favorite, three ways. A favorite is -200. Decimal: 100 ÷ 200 + 1 = 1.50. Fractional: 100/200 = 1/2. A $100 bet returns $150.
Starting from decimal. A price of 2.50 converts to +150 American and 6/4 fractional. A price of 1.50 converts to -200 American and 1/2 fractional.
A price you’ll see constantly. -110 is 1.91 decimal (100 ÷ 110 + 1 = 1.909) and 10/11 fractional. A $100 bet returns $190.91.
Reading a bet slip
When you place a bet, the slip shows your stake, the odds, and a projected return. Watch the wording:
- “To win $150” means profit. Your stake comes back on top, so a $100 bet at +150 returns $250 in total.
- “Total return $250” means profit plus stake. The profit is $150.
Same bet, two descriptions. US-facing books often default to “to win,” while decimal-first books quote total return. The distinction matters when you compare offers across sites.
Implied probability: what the price is really saying
Implied probability converts any odds format into the win rate the price implies. It’s how you compare a +150 underdog to a 2.50 decimal price without mental gymnastics.
- Minus odds: divide the number by the number plus 100. -110 → 110 ÷ 210 = 52.4%. -200 → 200 ÷ 300 = 66.7%.
- Plus odds: divide 100 by the number plus 100. +150 → 100 ÷ 250 = 40.0%. +170 → 100 ÷ 270 = 37.0%.
- Decimal odds: divide 1 by the decimal. 2.50 → 40.0%. 1.50 → 66.7%.
That percentage is the break-even win rate at that price. Bet -110 repeatedly and you need to win 52.4% of the time just to get your money back. Bet +150 and 40% is the break-even line.
One honest caveat: implied probability is a price, not a forecast. It includes the book’s margin, which brings us to the vig.
How the vig works
Take a typical two-way market: both sides priced -110. Add the implied probabilities: 52.4% + 52.4% = 104.8%. A fair, margin-free market would add up to exactly 100%. The extra 4.8% is the vig, also called the juice or the margin. It’s the book’s cut, built into both prices.
It shows up at every price point:
- -110 / -110: 52.4% + 52.4% = 104.8% → about 4.8% vig.
- -200 / +170: 66.7% + 37.0% = 103.7% → about 3.7% vig.
The vig is why “the house always wins” isn’t magic, it’s arithmetic. Every price on the board is slightly worse than the true chance implies, and the margin is the fee for placing the bet. It’s also why the break-even rate at -110 (52.4%) is higher than a coin flip’s 50%.
Books adjust prices constantly to manage risk and balance action, which is why a line you saw this morning may be different tonight. We cover how those moves work in our guide to moneylines, spreads and totals.
Reading odds like a shopper
Three formats, one skill set:
- Convert to a format you can compare. Decimal odds compare cleanly because they multiply; implied probability is even better.
- Compare the same market across books. A price of -105 at one sportsbook and -115 at another is a real difference over hundreds of bets. Our sportsbooks page tracks licensed US options.
- Remember what the number includes. Every price carries margin, so the implied probability is always slightly worse than the book’s own estimate of the chance.
Odds aren’t a prediction: they’re a price, set to attract action on both sides while leaving the book a cut. Read them that way and the whole board gets simpler.
